I bought my female friend a Christmas gift.
Why did you buy her a gift?
Christmas is her favorite holiday.
It's nice that you bought your friend a Christmas gift because it shows how much she means to you. Your friendship will probably be even stronger after you give her the gift.
It's nothing, and I'm also paying for dinner.
I hope that she loves the gift, and that you have a lovely dinner together.  I think it's great that your friend loves the holidays, and that you were able to make it that much more special for her.