The company can't withdraw their contributions I don't think. Otherwise she could never move job in her life and that would stop a LOT of people from working for them at all. No-one signs up to a job for life, people change, circumstances change, everything changes. I'm not a pensions expert, but I see them a fair bit at work and normally it's only if you leave say within 24 months they'll withdraw them if you have a really cushy deal they made purely to bring you in. One loop hole would be to take early retirement, then get another job after the pension payments have started.
As Ekona says, the contract will say it all. I highly doubt it though.