Best friend flirting with my boy….

I keep expressing to my so called “best friend” that she is flirting with my boyfriend and it makes me feel uncomfortable.

She tries to share food, drinks, and even weed with him.

I expressed to her and she blew up and didn’t speak to me for a month. I let her come back around and she still continues to disrespect me.

I had went to the store to get drinks and my boyfriend told me she told him “you should’ve never made her your girlfriend.”

Am I wrong for ending our relationship? I communicated with her once again about this shit and she just was saying “okay” and had an attitude.