...and having seen the negative results of this coz of an idiot family member not related to me by blood...
Don't get involved if there's a kid...you'll feel terrible if you bang her, her husband finds out, the family splits up and the kid is left somewhere in between...but affected for life. It's a real sad thing.
Don't mean to 'shrink' it, OP, just saying. Your thing isn't as important as that kid's life...and though you wouldn't be entirely to blame...you'd certainly have some responsibility.
If no kid, then I won't either endorse or condemn move...you're an adult and so is she.
Sorry...old guy...not religious...just seen the affect on a kid close up and it's not good.