Huh, you're the first person who's said Aspasia seems OP outside of sparring. It kinda makes sense for this encounter - HP% damage, occasional freezes, tanky enough to survive for a while all make her pretty good there.
That said, she has absolutely no support abilities, crit, mastery, or equipment, so she's pretty mediocre for most content tbh. I'd always take Sarah over her.
And yes, Siofra will definitely be lewdable, as well as the nymph getting introduced soon, may not be immediate though. I have an unhealthy number of ideas already LMAO.