When you fill out the paperwork at your FFL, one of the questions is, "Are you the actual purchaser of the firearm"? If you're not, it could be considered a straw purchase. I would contact Bud's directly before it ships to be sure of the legalities.

Should be just fine, the billing address is the important thing. And since its your address, you should be safe here.

If it goes through on Monday your are fine. if there is a problem have her buy Buds gift cards for you then use the cards to buy the gun

Usually the billing address should be the address of the purchaser. Buds will notify you if there is an issue. If there is, have your girlfriend purchase you a Buds gift card and then you make the purchase/payment.

It shouldn't make a difference though as long as the firearm is going in your name and you do the FFL transfer and DROS

Hi Ricardo It may go through. If it doesn't they will send you an email on Monday