Hey guys what should i do about this- retaliate or ignore?

my ex has been accusing me of talking smack about her when i know i didnt. what irks me is that without facts, she not only accused but insulted me as well. and for what? nothing. she tried to get a reaction out of me by saying that i posted my own questions on formspring and that im a joke because of that. should i confront her about it or ignore her? sorry if im overreacting, i just find it really hard to handle these types of situations. i need to learn to care less.