My mom has torn my family apart and I just don't know how to react?

It all began with her iPhone. Me and my sister found out that she has a secret Facebook page where she was basically acting really promiscuous and talking to multiple men and arranged a secret meeting to meet one of them in Vegas. She left her Facebook open accidentally and we found it, and told our dad. Since then it has been this whole roller coaster, and she has yet to stop using her phone. Now she is moving out, and we got in a huge fight yesterday because she wanted to go to some convention to meet up with more online friends today. Now I feel guilty because I said things I wouldn't have said if I had thought it through. It is hard for me to explain the whole situation, but I just don't know what to do because she is hurting our whole family and I feel so angry and hurt by that, but I don't want to ruin our relationship forever. She just doesn't want to put in the effort to make things better or to raise my 3 younger siblings, which really hurts.