Not going to deny that there might have been a bit of coercion or exploitation of Riker going on in this episode, but also, not having seen the episode in a long time, I don't recall Riker especially seeming to have a problem with it, which is perhaps the most important aspect to consider?
But he wasn't particularly enthusiastic about it, either. Here's the dialog:
RIKER: Now, will you help me?
LANEL: If you make love to me.
RIKER: What?
LANEL: I've always wanted to make love with an alien.
RIKER: Listen, Miss
LANEL: Lanel.
RIKER: Lanel, I really have to get going. All the other aliens are waiting for me.
LANEL: Oh, it's not so much to ask, and then I'll help you escape.
RIKER: It's not that easy. There are differences in the way that my people make love.
LANEL: I can't wait to learn.
(she takes of her spectacles)
RIKER: But it's
LANEL: It's your only way out of here, my alien.
Also, when he tells her 'next time I'm in the system I'll call you' on her question if they'll ever meet again, it's clear from his facial expression he's just deflecting giving a real answer.