Why offer any excuse, just walk up to the register and pay for your item. If the SA ask who you are buying this for, ask her why she would like to know. Answer questions with questions. I have had male SA's ask me who I was buying for. I just ask them why do they want to know, one I ask why are you making a pass at me.
If the SA ask if they can help and you need it, allow them to help you. You will be much more pleased with the purchase you make.
