And here comes inconsistency - from dialogues with her it shows that she’s not so sure about relationship with Tav (asking three times if you want to spent life together during different occasions).
I think you're very much misinterpreting this. It's not that she's unsure about the relationship but she has some serious self-esteem issues based on a lot of her dialogue in act 3. So she asks you to confirm it so many times because she's worried about you changing your mind about wanting to be with her not that she doesn't want to be with you.
