on 19-09-2023 10:58
on 19-09-2023 11:12
You need to cancel the account.
Guide: Cancelling Your Contract
on 19-09-2023 13:15
Bear in mind she will have to contact you if she wants to keep the mobile number
The easiest way for her to keep it is to get a PAC code and once used by her the O2 account would be cancelled unless she wanted to remain on O2 then the number would have to be migrated with the same result once she takes out a new contract