Hopefully your girlfriend's anger will blow over, but consider this a lesson learned. For one thing, IF her mother is actually having an affair, that's between her and her husband. It's not your business, it's not really your girlfriend's business, and it's certainly not the business of the person who informed you about it. Besides that, whoever told you about the situation may have been lying, and could have had some bad motive for it, like just trying to stir up $hit. I would have asked the person who came to me with the info, "Why are you telling me this? Do I look like I care?"
get out of this relationship before its too late.
no one should be hitting anyone.
bring her the evidence...
You should report her to the police for "Domestic Assault." They may not do anything but file the report, but she will have "a record" the next time.
May be she knew that and didnt wanted u to see her differently and ended up breaking with u. Try to to convince her directly or indirectly through your friends..But never tell about this affair to any your friends or hers! It will worsen the problem..May be leaving her moms affair aside will help u with ur love!
It is an irreparable mistake you have done. Except apologizing till she is convinced there is no other go for you.
tell her that you don't want to ruined her respect to her mother but you're just telling her the truth!!!!