Is your problem with how she plays or with the fact that she declined your advice to improve her play? Did you spend any time thinking about why she plays chess?
She may very well enjoy playing but doesn't take the game seriously enough, to let her losses negatively impact her and/or to seek improvement as a player.
Another possibility that you may have neglected is your advice may have been declined because of how it was offered. It's clear that watching her play is a source of frustration to you and she could have picked up on that frustration based on the tone and word choice in how you offered your advice.
I have a friend who has learnt chess and has been playing for three months. I watch her games and it is painful. She has a chess.com grade of between 100-200. I have a grade of 350-400. I had a BCF grade of about 115-120 in the 1980s but I stopped playing in the early 1990s. I started playing again when my friend took it up this year. I used to play league games for a club and tournament games. The time limits were something like 40 moves in 2 hours. I think I am at my level now because I win about half of my games when I play random people.
I watch my friend and she has a really bad attitude. Most games she puts her pieces where they can be taken and if her opponent does the same she doesnt take them. She likes to put her knights on the edge of the board. She also moves her knight pawns forward two squares so they can be taken. In about 50% of the games she leaves her queens hanging. She didnt like to castle and when I advised her to castle she would tell me it's a waste of time! She has started to castle sometimes but often she prefers to move her king one space towards the rook even when she can castle. She regularly gets her king chased around the board! An opponent will attack her knight with a pawn and she'll just let it get taken.
I have to admit that her opponents are not a lot better. The number of times I have seen mates in one not being noticed. The times I have seen stalemates is unbelieveable. Even when one player has a king, two or three queens and two rooks against a lone king they seem to move the pieces around at random without thinking of a system. When an opponent is moving a pawn up the board she will chase it with the king even when she cant reach it! I have seen her king under attack by many pieces and all she cares about is taking a pawn on the opposite side of the board!
When I try to give her advice she says she doesnt need my advice. It reminds me of a bricklayer who's walls always topple over and they just carry on.
I seriously dont think I could do a worse job if I tried to lose.
I know I cant help her but why does somebody have such a bad attitude at playing chess?