Negative effects of taking the pill a week longer?

Next Monday I get to see my girlfriend again after a month and a half of her being away. We were very excited until she counted her birth control pills and realized her special friend was coming the Saturday before. If she were to start the next pack immediately, instead of the placebos, for just a week, would there be any major side effects? We both really want this, but at the same time I don’t want to hurt her.