Best friends & Partners

My ‘best friend’ is the straightest girl out and never even thought about being with a girl, however she constantly has to have everything that I do including sleeping with multiple of my ex’s. She now is trying to get between my girlfriend and I have spoken to my girlfriend who says I’m being sooky and immature about being concerned and my best friend completely brushed it off and blankly told me that she talks to my girlfriend more than me and I shouldn’t have an issue with it. However recently on my birthday my friend apparently wanted to kiss a girl but would only kiss my girlfriend

I’m not sure if I’m over reacting by having an issue or if there might actually be something that someone’s trying to hide from me

Please help 🤷🏼‍♀️😭