my dad left my family when i was 4 years old. he came back for one night when i was 6 and tried once to call me and my brother when i was about 13, but that aside he's been completely absent from my life. no communication, no child support, leaving my mom to raise us on her own.
if she contacted you first with an apology, chances are she wants to make a change. but don't think that a new baby sister is going to be a miracle cure to save your relationship.
i don't believe in the adage "forgive and forget". forgiveness can be good, but forgetting is just willful ignorance. you can pretend you've forgotten something all you like, but you won't actually forget unless you're an amnesiac or have Alzheimer's. if she has a lot of bullshit to answer for, then hold her accountable.
