Initial Message issues

I'm liking the new messages application and have been playing around with it a little bit. I've noticed an issue however. I have an iMac running the new message application, an iPhone and my wife has an iPhone and an iPad. I've wrote her a message from the iMac that she receives on her phone but not her iPad. It also seems to have created a new thread which causes issues because it gets confusing as to which thread to reply to. This is also true on my phone; the message written from the iMac show on my phone in a new thread however. It seems like I may have a setting incorrect, and was wondering if anyone is having similar issue and could point me in the right direction.