I had a friend like this. I am very fit I go to Zumba three times a week; I love to walk and just roam around towns/ charity shops or the country side. She is rather overweight, has high blood pressure and walks with a sick. When we would go out, she would need to jump on and off busses or get taxi for the smallest walk (often one stop). She has a bus pass, I don’t yet. I always went along with this as, I understood how hard it must be.
She kept asking to come on my solo day trips and I never wanted to be unkind so I would always say yes. The last one we went on, was nightmare. She refused to sit in the disable seat on the train as it went backwards so she was trying to get up a crowed, narrow train with a stick , asking people to move out of a seat that was facing forward. She had to get a bus to get to the town centre, but refused to get on certain busses as the seats were too high. She didn’t want to go anywhere, expect from café to café. I am not one for sitting in cafés all day. I suggested she sat in the cafe while I looked around but she got upset. I offered to find a wheel chair and she said I was rubbing her nose in the fact I was fit and she wasn’t. I really didn’t mean to be unkind. She complained the whole day that I was too fit and it wasn’t fair, even though I was walking a snail’s pace. She complained that she was tired, her back hurt over and over and she needed to find another cafe. She refused go into any shops and I had to keep finding her a bench to for her sit on, then I couldn’t look around any shops as I felt guilty leaving her outside. I suddenly realised that it didn’t work, and while, I was happy to still do her thing (sit in a café for most of the day) including her in my thing didn’t work.
She has since ghosted me as she said I was ridicules doing Zumba and running about like I do, at my age and it wasn’t normal then she just blanked me after years of friendship.
I am sure your friend isn’t like mine. but I think you should talk to her, be honest and say it maybe too much as we will be walking a fast pace/ fitting a lot in, (let her chose) give her the chance to either find a way or decline but be also happy to do things that she can manage easily now again.