First of all, there are many kinds of lies, good-intentioned and malicious, with different starting points. No one can say that they have never lied since childhood. However, when making friends, some people are cautious and some are casual. It depends on whether the friend you are talking about who is lying has been lying for a long time. To be honest, telling a lie requires making up thousands of lies, which is very tiring. She lied about her grades, there are several possible purposes

Firstly, she doesn’t want to lose her position in the dormitory and doesn’t want to be the laughing stock. Of course, you said that you two are the best, and she may also know this. I don’t want to lose your “friend” either.

Secondly, everyone has self-esteem. She has a strong self-esteem and regards her own self-esteem as more important than the sincerity between you.

So it’s up to you to decide whether it’s worth a close friendship. You have a very good relationship. She understands your affairs and you understand hers. Try not to be too extreme and keep in touch while maintaining distance in your heart. Hope this helps you