I remember this movie which should be from the 1990s I believe. I describe whatever I remember, it may not be 100% accurate at some points.
It’s about a woman who had killed a previous husband to get the money from his life insurance. She has been accused but not convicted. She moved to a different town where she starts a new life and nobody knows her background story, but again with a wealthy man, she starts the same plan all over again. I remember there is a murder (or attempted murder) during a holiday, where they use the fireworks to cover the gunshot.
I remember the actress had a heavy accent (I would think Southern, but not sure). Her lips weren’t natural, you could tell they had been filled, I believe you could tell she had a nose job done too. He had dark brown hair.
Maybe “Black Widow?” I don’t remember how the character killed all her rich husbands, though.
https://www.imdb.com/title/tt0090738/?ref_=fn_al_tt_2
I doubt this is it, but this is the first thing I thought of. It’s not really what you said but had similar details that could be mixed up.
Unfortunalty none of those, bit thanks for the guesses