Mom's requesting we take what will very likely be her last trip anywhere. How do I handle this?

Mom is 82, in bad health (undergoing 5th chemo treatment today for stage 4 lymphoma, has hemolytic anemia, diabetes), but has always travelled with husband, and later with family or even her CGiver and CGiver's son, to London.
I've put off her request to go with her for the last several yrs because of her lack of strength and mobility. She had little wind power, little leg power, tho both lungs and legs function "adequately", and pushes a wheelchair to get around, sits in it when necessary. No, won't use the little combo seat, wheely thing in the house!
Anyway, she spends all her time at home in bed, eyes closed listening to TV. She'll do same in London, tho she'd like to go to a couple of places. I know we can have assistance from almost every "door" to "door", cabs when needed, etc. I can probably check the little combo wheely chair (sorry, I canNOT remember what to call it!!!!) and use that, but I wonder if I should consider renting a wheelchair...?

I jump ahead.....the doctor will advise by month's end, I think, if she needs another treatment. She has told him about wanting to go. He says she's doing well. I've not spoken to him yet. (Oh yes, she's in TX, I'm in CA), but will do so after this week.

The real, logical me says this is a no brainer. There's no way, no reason, she can't do it and shouldn't do it. But then a gentle part of me says, if the Dr. says she "could" do it, then it's really up to ME and what I can arrange FOR her isn't it? And what responsibility I'm willing to assume? Oh, just made me think......for those of you who know my case....how do I handle this since I'm not her POA med or financially? What if?

Any experiences out there?