Mistake in the timeline

Rating: 10/10 (15 December 2018)

So think about the altarnate universe s gwen stacy.She s first appearance in the movie was before miles got his powers from spider.But that scene was before portal s opening scene so It does not add up.It cant be the miles universe s gwen stacy because they first met in the film class and he did a joke in there that she mentions this joke line before she leaves so how did she arrive so early ????!