I'd also like any response where my character can finally tell him she loves him. Something like "I love you and only want to spend my life by your side." Or as an alternative to asking to become a vampire, asking to spend an eternity with him alone. "I wish only to be yours forever." Then at the end of the turning scene, what the narrator says already confirms your wish.
Yeah, great options! I think Astarion would love Tav's words, "I wish only to be yours forever.", it would fit perfectly, considering he wants the same thing himself.