What are signs someone is not a good friend?

In the last few months, I met a very sweet person (let’s call her Anna) who would tell my group friend that she didn’t want to invite her best friend because “she’s too much.” Anna would say it nicely about her best friend. When I finally met her best friend on a 5 days trip, I thought she was very nice and genuine. She was open and outgoing.

I recently realized how fake Anna is. She has caused so many problems and played victim throughout the process. She even tried to sleep with my best friend’s husband.

I also thought about how she talked about how she liked her roommate 1 and disliked roommate 2. Then suddenly switched within a few months later and said roommate 1 was so toxic and she liked roommate 2.