You put a condom on then flipped it over what are the chances of pregnancy?

I assume you put the condom on on the 'wrong' side so it didn't roll on properly and then realised your mistake and put it on the correct way.

Unfortunately, some seminal fluid reaches the end of the penis before ejaculation so there is a chance of pregnancy. The spermicides on the condom might help, but there is no guarantee.

I suggest your girlfriend goes to a pharmacist as soon as possible and asks for a 'morning after' pill.