She has trouble managing money and is constantly broke. Any attempts to maintain a budget are futile.
This is normal, you can't fix this.
Whenever she needs money and i don't immediately 'rescue her' (by sending her more money) then she becomes more hostile.
She would not respect you for rescuing her, as that wont fix the problem, due to first problem, she will end up back at the start and hence your attempt to rescue will be deemed a failure.
You can't stop a river from draining water by adding more water you just create a bigger river.
In answer to your first post, don't overdo active validation, especially by telling her how YOU feel, she doesn't believe you can and you are simply saying she is wrong. To her that feels like you are not listening.
Instead listen to her and ask questions how she feels. Prompt her to allow her to lead discussions, dont try to steer or direct them. This approach focuses more on not invalidating, rather than trying to positively validate, which as you have found can sound wooden and is fraught with trip ups.
Above all don't confuse emotional support with rescuing as that creates an unmeetable demand