If you search the net there are lots of different providers who charge between 7p to 10 p per minute to call a Phil mobile from a Uk mobile. Usually you have to buy say £3 or £5 credit in advance by SMS, and you are sent a PINi no which you have to use when you dial. You call a London number or 0845 number input your pin when requested and then input the international number and you get connected.
As Steve R said, it's easier if you get her a smart phone with a web usage package, then she can use YM,or any of the chat services on her phone. If she uses a service like E-Buddy or Nimbuzz she can create one account and log into all the chat services at once rather than logging into each one separately
