I am the practical one. I would encourage your Mom to buy a nice used bike to start. That way she can figure out if its for her or not- without alot of expense. I would buy a light weight cross bike or mountain bike with slicks - not knobbys. I would change the grips to make them padded and comfortable. I would also sit more upright. She needs a frame that fits comfortably and she can get on and off the saddle easily. Gears are important too. She will want enough gears to spin easily. She should look for a bike that is easy to shift - not all the shifters are easy to reach and maneuver with arthritis. My daughter is 13 and has juvenile rheumatoid arthritis. Certain movements create different types of pain - so she will want to try several out to see where the pressure points are for her. My daughter has trouble with her ankles and fingers right now. And she certainly should pick a style and color that make her grin from ear to ear. Good luck - let us know what she decides.