Should i tell her to back off?

i met this woman and it was innocent from the start because she has a gf (9 year relationship) so immediately i knew to keep my hands to myself and respect that. well we have hung out a few times after and the last two times she has been very touchy feely. she hugged me really tight for a minute or so, put her hand on my thigh, touches me or pokes me, and is avoiding eye contact iwth me to the point she is wearing sungles. i could REALLY fall for her, but i feel guilty. i haven't been touching her or anything but i definitely don't stop her. she talks about her gf a lot but doesnt seem very happy with her. the thought of not seeing her again is suprisingly devastating...there really is something between us and i don't wnat to back off but at the same time i don't want to be the reason she might leave her gf? i'm so lost!