It should be your choice whether you want to forgive her or not. You can handle this situation by communicating, if you feel that you should at least listen to her and ask her why she did so, why she left you and your daughter behind then you can give her a chance to explain herself, after listening to her you can decide what you want to do. Do take care of your child’s future, and make sure this thing won’t happen again, it will affect your child a lot. 
Communication is the key to solving half of your problems in life, talk about the situation and take action accordingly.