Any transaction date and time u have ?IMO,

A/C Scan the receipt,camera photo,if they no keep receipt then ask the girl C go bank and request a transaction slip printed from bank and verified by that bank and take a photo or scan to u.

If all they duno , just need the girl C contact , wat ever u ask her , u juz request bank slip from the bank. The bank can assist account holder in getting own account details as well as the amount go into whose account and so on. No matter she bank in by check or wat sure can get full details. If he said cant contact with C , thn " ASK HE WAIT TILL CAN CONTACT C"

So bear in mind , C is the important ppl. And u can go ur bank ask for a particular monthly bank record and thn compare with her bank slip.