I'd also put the onus on her to choose, then you can't be blamed. Also, the price you pay and the deal you get (on "running costs") is as important as the actual phone.
Thanks guys....it's her money and she's made up her mind that's what she wants....i just need to soften the blow a bit by making sure she gets a decent one.
A young family friend staying with us at the moment has just bought this Blackberry from the Carphone Warehouse on pay as you go for £119. She's quite happy with it. But like you I know nothing. I still use an old Nokia which I switch on when I need to phone someone, which isn't very often.