I like the clothes on the left. As you say, it hints to something a lot deeper going on in the piece: She’s not just a random alien he’s passing, she’s dealt with humans a lot in the past. Also, because those clothes are practical like his, it puts them on an equal footing. The more “sexy” you make her clothes, the more you just turn her into a sex object, and then the power dynamic becomes really trite and boring. (imho.) In fact, I’d suggest keeping the human clothes and giving her a rifle or a pistol. Then it really puts them on an equal power level, which I personally find the most interesting. But hey, that’s just me, good luck with whatever you decide.
p.s. love the face “tattoos,” hope you’ll do more of that on the body too!