I agree that a fitting is in order. You will be amazed by how much further you can go with the same level of effort on a bike that FITS (ask me how I know...).
Can I just say how proud I am of you? My mom is 66 and has given up. She is fragile. We joke about what a klutz she is (a year ago she broke her neck tripping on a step while going into the house), but it's really sad. She is physically so weak. She has asthma, yes...but so do I. I refuse to let it make me an overweight invalid (Ok, I am overweight, but I'm kinda kickass, too).
I hate that she won't even try to make herself stronger and healthier. Her excuses always start with "at my age..." There are people her age who have started running and ended up running marathons into their 70s and 80s. She is throwing away so much. And she fails to realize that so many of her ailments are because she is inactive. Her asthma would be better if her lungs were given regular workouts.
I love seeing women 10 years either direction of my mom who are not using age and/or weight as an excuse. I wish my mom had internet access so I could send her links to threads like this. She needs to see for herself that her only limit is herself.