I hate not having a reliable means of transportation

I have an agreement with my grandma that I can use her car whenever I need it, as I don't have one of my own, as long as I drop it off at hers whenever she needs it and pay for fuel myself. An agreement I honored for a long ass time. Grocery shopping day is on Friday, so as I have a shitton of appointments myself this month, we agreed I'd drive her (her driving capability is declining anyway), help her and then keep the car afterwards.

A week ago, she told me she had an appointment on Thursday and might need the car then. But she said she'd get back to me, as there's a chance my mom would drive her, as they had some kinda arrangement. She never got back to me. And honestly, I forgot. I had appointments every single day leading up to friday and was mentally spent.

Thursday passed, Friday came, she ignored my calls. My text asking if we're still on for grocery shopping went unread. Saturday morning came and she finally answered my call. Didn't even let me say anything just responded with a snippy "I'm mad. I needed the car on Thursday. Drop it off for me today, whenever you see fit." And then hung up midway into me asking wtf. Guess her arrangement with my mom fell through after all. But she also never called or texted to let me know.

Yall, she's been declining mentally, but I'm at my wits end with her. She's already been pissing me off with some of her behavior regarding me. She's getting old, so I give her some slack and never say anything, but this one was my personal last straw. I don't have another reliable means of transportation right now. I have a motorcycle, which I love, but I'm still weakened after a pretty major surgery and don't feel secure enough yet to get back on it. I can borrow my sister's car, but she needs it herself for commuting. I could take my parents', but it's a huge ass car that I don't feel comfortable driving. But I also don't wanna have to put up with my grandma's constant bullshit, just to be able to get from A to B. Buying my own is out of the question right now. Uber or other driving services don't really exist in my area. I wish I didn't live in the middle of nowhere so that cycling could be an option.

I'm exhausted, physically and mentally, still in pain at times, have 5 separate appointments next week again, 4 of them medical, and I really dont know how to juggle all of it. I don't wanna have to beg my grandma and get on my knees before her so I can keep the car, even less so when she's in her pissy mood, but I also don't wanna have to beg my friends and family to drive me everywhere. My one option is to get back on the bike and drive carefully so as to not strain my surgery site.

I swear to fuck, I'm so fucking tired...