I am older than your Mom (58) but started my big weight-loss and lifechange stuff when I was a little younger, at age 46. I regret now that I did not include a regular exercise plan, other than walking from the beginning, but I was living in the high Arctic and resources for this were pretty much nil.
I started at at 5'6" and somewhere between about 235 and 240 - didn't weigh exactly when I started. I was riddled with some pretty serious illness, including autoimmune disorders and pretty severe IR/reactive hypoglycemia, so these were factors too.
I hit goal weight - which I had loosely established then as the weight that I sort of naturally corrected to and that I could maintain comfortably. That weight became 148lbs as of about Sept of 02. By that time, I had moved back to northern CA and was doing serious sortt of race walking for about an hour daily. I have now dropped to 140ish in the last year, after alot of healing and lifestyle change over about 11 years.
Moving forward to age 52. I had a friend I worked with who went to Curves for Women and really encouraged me to check it out. So, I did. And it was one of the best things i've ever done. If I could go back on this journey, the one thing I'd change is that I'd have started going to Curves from the beginning. I now teach Zumba in the Curves Circuit 4 hours a week. (I'm an independent conractor, so I am not advertising here for Curves.)
Curves will work for any woman of any age with any level of fitness and that is one of the things I really love about it. I work out with 20 year olds, 75 year olds and I give a ride daily to 94 year old woman who has been going almost daily for TEN YEARS! She is an incredible inspiration to me and other women.
The basic program is three times a week with rest days between each workout day. It is a strength training/resistance circuit which utilizes hydraulic machines with recovery stations between each strength/resistance station. You progress at your own level - to an advanced workout, if you want. And your'e in and out in 30 minutes. Some women like me have worked up to a very intense workout, many are in the process of pushing themselves just a little bit more, each time. I go daily, varying my workout accordingly.
A really wonderful aspect of Curves is that it becomes a support system for women in which they get cheered on by other women. Important, supportive relationships are formed with women who can identify with each other. An important assest in weight loss, lifestyle change and then the all important weight maintenance is a SUPPORT SYSYTEM.
Curves is also THE most researched organized exercise program in the world, which includes their weight loss eating plan. (No, not Paleo, lol!) But, Curves was waaaay ahead of the ball when years ago it incorporated a lower carb plan and a self assessment so that any individual woman could choose the plan she felt would work best for her.(And no, choosing one of their offered diets is not in any way required.)
You can read about some of the research here as well as being able to pull alot of research on it off the web. The original research was done by Baylor Uni and the recently changed to Texas A and M.
The bottom line is, whatever your Mom chooses needs to be something she will keep doing.And it's important for her to not feel overwhelmed and uncomfortable. Curves is a comfortable environment for women who would NEVER go to a regular gym and many of whom who originally HATED the very idea of exercise. There will be plenty of women there her size and age and women like me who came from exactly where she is now. It is also simple and any woman who joins will be taught, individually exactly how to work out on each station, no matter what her present physical abilities are, and monitored during each workout with staff always available.
Cost probably varies a bit by location. The cost at my Curves is 34.00/mo for unlimited visits. All Curves have early and extended hours.
Oh! There's also a promotion that may still be going on which is a free pass for a week to see if she likes it for NO COST. You could also go with her - at least at my Curves this is how it works.
I am happy for you both! Sorry to babble on a bit, but it is a subject i feel strongly about. A sobering statistic to be aware of is that 95% of all those who lose weight on any type of weight loss plan gain it ALL back, and many gain even more. So, choosing for what I'd call compatibility, support and longterm success is important.
I am now even working with just a couple of women in my Curves and inching them toward paleo/ancestral eating.;