@Wagner Alcivar , if your girlfriend will be occupying the property with you, then, you should have no problem but not as a non-occupying co-borrower.
@Wagner Alcivar just in case it matters, if you would like for a non-occupying co-borrower to be a part fo your FHA loan it is allowed but it changes your down-payment to 25%....so not really a reason to do it.
@Wagner Alcivar , sorry, if we were not clear. If your girlfriend will be co-signing and also occupying with you then no problem. If co-signing but NOT occupying, then you will need to put down 25% down-payment as @Andrew Postell mentioned. It's the occupancy that will most likely matter to you most and how you proceed with your bank. Hope that helps.