I'm going to go against the grain here and say that, in your position, (which I sort of am - I'll explain in a minute) I'd continue to get on with my life without her.
My dad's parents have not been a part of my life since I was 15. Big fallout - they said some VILE things and told some horrible lies and really upset me and whole family. They then turned all dads relatives against us. We had no contact with any of them for over 15 years, until sudden death of a relative, when mum persuaded dad to extend olive branch.
Olive branch accepted. Mum then wanted us all to, well, to not be not speaking any more iyswim. So we are not not speaking! But nothing has changed. We still have no relationship and never speak from year end to year end! We have nothing in common.
we exchange christmas gifts with dads parents (well, they give us a gift and I do not want to feel I owe them anything so I get one back! It's like an exchange of hostages ), but have no contact with anyone else ever. They are nothing to us and we are nothing to them. And none of us have ever lost anything by it.
Too much time has passed and too much was said that can never be unsaid, done that can never be undone. I am NOT a believer in Thou Must Embrace All Relatives And Be In Their Life. I think that is bollocks. Total bollocks.
So I'm afraid that in your position, I'd delete the email and get on with my life. Sometimes, you put a person behind you for a very good reason, and the fact that they are biologically related - irrelevent. this whole family at all costs stuff is a sack of shite, imo. You don't owe someone ANYTHING because of an accident of birth.