She can do the meds herself but her attitude is” I don’t feel like taking them today”. She’s in denial that she’s 95 and needs help. Add to all of this is that she’s not the most cuddly, warm person on the planet. She goes out of her way to make all of us feel guilty and adds nastiness on top.
Regardless of the meds there are foods that help with most chronic conditions particularly spices . So look them up and buy bottles of them for her drawer so she can pour them on the food when it arrives. That is one example of where doing something on her own, even to a small extent, can do wonders. The most stress and ultimately negative feelings come from not having control over one's life. Getting old is not controllable and getting ill is not always controllable, but having a feeling of control of something is the key to alleviating stress.
Obviously she can also try to control things in a negative way which sounds like what she is doing. That transfers the stress onto you and your siblings to the extent that she can make that happen and you all let it happen. That's why some small efforts, even when she tosses them in the trash, can make a big difference.
Your control can start with a plan which can start with ideas you glean from the internet or people you talk to. Even if it fails 100% it still alleviates you from the bad stress of not having control over the situation.