You can't really "chat" with older iPod touch since they don't have microphone. If you want to just chat (no video) with her using laptop, you can use Skype. AFAIK, there are currently no way of doing video chat on iPhone 4/touch 4g without using FaceTime. There's been rumors of future support for using FaceTime with folks on computers (via iChat, for example).
There may be solutions if you jailbreak the touch, though I don't know since I've never looked into it.