I'm Dming an adventure with some of my good friends and one of them has made a really, incredibly boring character. I offered help during the creation and insited she do it on her own which I was fine with. Shes relatively new in the world of dnd so Im helping where I can to make her more comfortable but her character is one that refuses to interact with the group and stalks from a distance or goes off to do her own thing instead of joining the group. Her character barely talks and she seems at a loss of what to do because the other characters have played before and semi know what they're doing. I started the campaign in a casual setting and most of the PC's introduced themselves to eachother and her character just sat quietly in the corner not saying anything. We are only one session in but I want to make sure she feels included and honestly I dont want to have to create a whole other adventure just for her character (Which seems like its where this is going). So, I suppose my question is how do I help her come out of her shell and be more confident? How do I help her improve her isolated character? 

Some of my players had the same sort of problem. First, I gave them the list of questions for them to answer about their characters. They’ve shown a lot of positive feedback for it and I go through this process with each of my characters. Hopefully it will flesh out your players character so that she feels more confident role playing it.

1. 2 bonds, flaws, and ideals that you have written BY YOURSELF. No dnd beyond help. Remember a bond and a flaw can be the same thing from different points of view, this should illustrate your character’s point of view.

2. What is one major, LONG TERM goal for your character? What is a minor, insignificant goal for your character?

3. What is 1 thing that makes your character laugh, 1 thing that makes them cry, and 1 thing that makes them blind with rage? Why do these things provoke these reactions?

4. What is your character’s favorite way to kill an enemy? His favorite way to save an ally? Does he like or dislike killing enemies or saving allies? Why?

5. Your character gets 1 free with spell with no risk of bad or
unintended consequences. What does he wish for (give it a good think. “Unlimited power” is not a good think).

Secondly, I would use NPCs to directly engage the character. See if you can get some conversation with her, draw her out of her confort zone a little. 

In the end it just takes time, and she will start to roleplay when she’s ready, just encourage her and let her find her characters voice. Hope this helps, best of luck!

If your other players are okay with it, you might want to have your current story focus on her in the short term or rejigger the story to specifically include some element of her background. I had the same issue with a player and I took one of his background ideas to create villain in the story he was invested in finding. Then later had a part of the story involve his hometown and aspects of his past. And I just sprinkled that in so it didn't distract too much but at times did shine the spotlight on him. You'll find players get move involved and out of their shell if they feel a character goal is intertwined with the story.

Another question they should be able to answer is "Why is your character adventuring?"

Edit: and did you have a session 0 where you talked about expectations?

I think jBagnoli's idea is a great idea. Have the NPC's direct their conversation through them after taking particular interest in them for some reason.

ie

NPC - "And who are you lass?"

Character - "Um.. I'm _______"

"Is that a Waterdeep accent I detect? We'll I'm from Sea Ward myself! I can't tell you how nice it is to hear a familiar voice....." etc

You can do the same with race, class or background. Drive the game through her initially to bring her out of her shell.

In the end, make her a focus - over hype any successes, reward NPC and other player interaction etc - and she will grow in confidence.

I think you should let a new player be a little basic. They'll learn RP as they go, figure out what makes a character fun for them, and since they're playing backstory-lite at the moment, just let them know that if they do think of something they wanna add as they get more used to playing, to talk to you about it to see how to fit it in. Then maybe they get more in depth when it comes time to roll the next one. 

You've got some of the best advice from people above:

• Find something, within the story/world, that you can use to put the focus on her.
• Give her a few questions that she can answer to help flesh out her character's personality and background.
• Make sure she gets the spotlight even when she's being reclusive.
• Don't let the other players, purposely or accidentally, overshadow her accomplishments.
• Understand if it's just her personality, or if it's a matter of getting comfortable with a social game.

I have a player who's very quiet on my stream, she's more open when my wife is DMing vs me. I've learned that it's, in part, due to her personality and she's just a mousy person. I watched and listened to my group as she played before making any adjustments to how I treated her. First thing I ended up doing was making her the focal point in a situation where she had to be the active player. The setup was accidental, but the situation was perfect, she was the only one in the party who was the right race to help out. It made her uncomfortable, but she did her best and I rewarded her for the attempt. The second time was to get her active in a story line where she had chosen to stay put while the rest of the party went out to do their various activities. I used that as a moment where I could insert her into a major story point. 

She's still quiet and very reserved, but I do everything I can to make her feel like her choices and actions have impact. I help embellish her actions so they sound more heroic and effective than what she's describing. I find ways to ask questions so that she can put more of herself forward, and I keep trying to get more information about her play style and character information. Slowly integrating her more and more into what's going on rather than let her sit on the sidelines all the time. I don't do it every session, but I do try to call on her by name each game so that she doesn't feel glossed over either. She's playing her first games ever, so it's a matter of helping her find her feet and become comfortable just going with what comes naturally.

Be patient and nurture the player, they'll come out of their shell in time. 

I did, I've been trying not to go too hard on her because she's very new to the game while trying to help her interact. I'll give her or help her come up with a goal

Thank you for your advice! I'll try it out before our next session to help her flesh out some more and come out of her shell!

I have a similar player, though they are an experienced player, she takes some work to get involved in RP. When I ran Dragon Heist and we worked on her backstory, I suggested a tie to the Temple of Gond, and added a faction quest for it in Chapter 2. This way there was an NPC that then singled her out for help (with the groups assistance too). Then the faction quest had at least one skill challenge that she was the among the best in the group at. Afterwards, when they had to help chase one of the McGuffins, she could also feel special by knowing exactly where to start looking. It seemed to work pretty well and kept with the flow of the module.

So the TLDR would be: work with her on her backstory and make sure there is a hook in it that you can use for a few future encounters.