ipad2 iMessages

I just got an iPhone4s but have had an iPad2 for awhile. I have an odd thing with iMessages.

I logged into iMessages on the iPad with my duaghters email so that we can text each other. If I send a message from the iPad to my phone number, I do not recieve it on my iPhone.

BUT!

If I send a message from my iPhone to the address associated with iMessage on the iPad, the iPad receives it and then we can message back and forth.

So the problem seems to be initiating a message on the iPad. If it receives first then it can reply to messages.

Is this how it should work? Doesn't seem like it.

I'd like my daughter to be able to send me a message without having to reply to an old one or in case the old ones get deleted, etc.

Thanks!