If the car was still on HP when she was bankrupt then it was not part of her bankruptcy estate as it did not belong to her, but to the finance company. Was she still making the HP payments while bankrupt? Has she finished making the payments - i.e. is the HP period at an end with no arrears due? If it is, then the car is now hers, but if she has nothing in writing she needs to confirm this with the HP finance company.
If the Official Receiver had intended that she should not be allowed to keep the car while bankrupt she would have been informed of this. If this is the case, she needs to contact the Official Receiver's office.