Best answer by Dennis
If she is not with Koodo, then it should be ok, as she can port her number over from the other provider later on.
Are you a current Koodo customer? (If so, you can buy a phone, outright, just for her)
Are you getting the phone on a tab? (putting a phone on tab means you are buying her a liability that she will need to pay back... just FYI)
If you open the account it will have to be under your name and then you will have to go to a kiosk to transfer ownership of the account (with appropriate ID)