My gf is insecure and I don’t think I can handle it anymore

Pretty much the title… For starters we been together for over a year and she was always insecure and I use to be able to handle it but it’s gotten to a point where it’s ridiculous! My coworker called me yesterday because I forgot to write down the money I had taken over the shift at the register because we had to deal with an extremely dumb but also funny situation. My coworker made a funny joke regarding that situation(which I told my gf about when I got home) and I laughed, and I proceeded to tell her how much. My gf was then upset that I was laughing and then proceeded to tell me if I stopped liking her to let her know so she can go on and kill herself, she has stated multiple times if the relationship ends she’s just gonna kill herself. I’m not even sure how to approach because when I tried to break up with her earlier she told by doing that I was directly telling her to kill herself. I’m really on the verge of completely checking out the relationship completely because this has been a constant since the relationship started