Hi
The AIM side of iChat can send SMS messages to a phone.
There are some limits to this though.
1) The computer has to be set up as if it were in the Untied States.
(System Preferences > Language and Text)
The Phone definitely has to be in the United States but also has to be one a carrier that supports AIM's SMS Forwarding.
If you can satisfy these criteria then the phone number gets added to an AIM Buddy List as if it were a Buddy with a leading +1 country code added (even though they never rolled it out further)
In the form similar to +1234567890
Your daughter could also use AIM express on a Mobile (She would then need an AIM valid Screen Name.)
Depending on the Apple ID she is using in iMessages it may work with a web browser login.
At iChat 6 Apple had the app also perform a login to me.com which then allows the AIM login to "See" the password.
As a Consequence to this extra security level check @me.com names (and @icloud.com names) cannot be verified On Line in AIM Express of the AIM Settings page
If she is using an @mac.com Apple ID then she will be able to login using the AIM Express.
IF you have GoogleTalk IDs then this could mean she could "Chat" in a Browser logged in to iGoogle or Google's Web Mail page.
Facebook and iChat could also work.
Facebook, like Google's GoogleTalk needs the account set up for "Chat"
As it is a Jabber server you can use a Jabber ID (GoogleTalk or Facebook or Other)
The Skype Mobile app and the Mac version should be able to exchange text chats the same way iChat can (i.e it should not cost any more than the data traffic she is already using.)
It should not needs to go through the SMS channels of her service provider.
10:25 PM Monday; November 19, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously