Which feat to choose for my arcane trickster melee charging rogue?

Hi, friends!

I have to choose a new feat for my Arcane Trickster Rogue, and I can choose a feat from either 5e or 5.5e. I desperately need help choosing. 

The feats she already has: 

• Charger (+10 Speed when Dashing. Charge Attack: Run 10 ft in straight line and add 1d8 extra damage to Melee attack)
• Fey-Touched (New spells: Misty Step and Hunter's Mark)
• Piercer (Reroll piercing damage roll once per turn. Add one piercing dam die when critting.)

Some background: Her signature fighting style is charging ahead in combat for extra damage with her rapier casting Green-Flame Blade for extra fire damage and disengage to get out of reach. She does not have a high health pool, at 67hp. She's now level 12. She's got 20 in dex and 19 in Intelligence, which means that preferably I would like to get an increase in int. 

The feats I am considering:

• Shadow Touched (5.5e) Intelligence: +1. New spells; False Life and Invisibility. This will help me as a front fight charger, in terms of hp and an added elemental of magical surprise.
• Elemental Adept (5.5e) Intelligence: +1. Ignore Fire dam resistances and treat every fire dam roll of 1 as a 2. Will help my spellcasting and my Green Flame Blade attacks (as well as Firebolt) which I use all the time as part of my normal melee attacks.
• Mobile (5e) Speed increase 10 ft. Difficult terrain cost no extra speed while dashing. No provoking opportunity attacks when making a melee attack. This helps my playstyle immensely! But I wont get an increase in Int and the other might seem like a better choice?

• Dual Wielder (5.5e) Strength +1. Dual wield and make an extra melee attack as a bonus action. Strength increase is not that important to me, would be cool to be able to attack twice, but then my precious bonus action would be used. So would be cool, but the other feats seem like a better fit?
• Lucky (5.e) 3 Luck points, used to add a d20 to attack roll, saving throw or ability check. Just a really good feat, but maybe not as relevant as the others?
• Tough (5e) Gain 24 extra hp and then 2 extra hp per level going forward. It would just help to have a bigger hp pool, but Shadow Touched might be a better fit, with False Life.

Thoughts anyone?