So it does seem when your mom has asked for help it hasn’t always been available so it’s no wonder she has lost a bit of faith. However it sounds like you have stepped in a lot since then which is a lot for you to take on and it’s having a negative affect on you.
Is there any way you could speak to her care provider and explain how your mom was struggling and had even CONSIDERED getting the medication from other sources to see if they can help without dropping her in it? I know they would consider health risks when prescribing but usually they would weigh up the pros and the cons, and it sounds from your explanation that there are more cons when your mom doesn’t take the medication. The other thing I would consider is that if you keep protecting your mom it might be stopping you both from getting the help you need?