Love triangle between me, girlfriend and friend?

I suppose it’s not a love triangle but it feels like it. I love my girlfriend and she me, her friend likes me a lot, and they’re both friends.

I (M22) must also preface this with the fact that she’s on her period and that this friend (F27) is married and I liked her before I knew she was married, which was only for 3 days from when she started working. My girlfriend (F22) and her are really close friends at work. I also have a few people crushing on me that my girlfriend is happy to hear compliments from, but it’s her friend that she’s not happy with.  

The problem started when my girlfriend said she had a list of good traits and bad about me, and I wanted to know if any of the bad ones I could fix. Then she said there’s her friend (the married one) who keeps giving me compliments and wants my attention. The fact that I’ve liked her in the past and say nice things about her (as I do with everyone) makes her feel insecure. She can also feel her jealousy when I show affection to my girl on her break.

So we talked and I said I won’t visit her at work and compare my girlfriend to her since her friend gave us food and I asked if she could cook something like this, alternatively take cooking lessons from her friend. Then she told me to add her and take cooking lessons from her and that she can’t trust me when I say I only love her, because I used to like her friend and talk about her when my girlfriend brings her up, that she feels stuck in the middle.   

The thing is, I love my girlfriend and couldn’t think for a second to cheat on her, and especially be a homewrecker. This friend of hers is emotionally immature and has her own problems with her husband, my gf said it herself. But I feel like she doesn’t trust me and I feel hurt that she would even think so low of me. It feels like my loyalty is being tested.

Another thing I almost forgot: her friend is older than us and in her culture it’s not okay to stand up for yourself as a younger for some reason. I can’t say much about it cus I don’t know enough.  

Am I trippin? Am I overthinking that she doesn’t trust me? She trusts me enough to share this insecurity with me and I boiled it down to her not trusting me. I used to think about her all day outside of work and she kinda stopped that. Rather, I might’ve stopped it.

TLDR: gf is uneasy about her friend I used to like (before gf was in the picture) who keeps talking about me to her. She says she can’t trust what I say about her even though we’re together.