Another multiple ID, multiple device, multiple phone number iMessage question

Wife just got a new ipad mini. She has an iPhone 4 with ios 5. I have a iPhone 5, and ipad 2 (running ios 6).

I set up a new apple ID for her ipad. iMessage working ok to that gmail, which I associated with iMessage. Is there a way to associate her iPhone cell number with that new ID so she can be receiving the same messages on her phone and ipad? Or can we go back to the common/old apple ID, but use only her cell phone number on both for her?

Been playing with this for a couple of hours, but I thought a question here might help. Thanks.

 

Thanks. Does that mean one icloud account can't send/receive messages from two phone numbers? I like the idea that all our icloud backups are under one account, although having a new icloud account would up our storage. Would she still be able to stick with her cell number and old icloud on her iPhone? And wouldn't that mean that we couldn't use the same photostream?