Hi Sundie!
From my own personal experience, I think WATP workouts are a wonderful way to begin an exercise program, and they are what started me on my weight loss/fitness journey!
I have the WATP Epress 4 Mile Super Challenge, and when I started with this tape I weighed 235 pounds and could barely complete the first mile. I worked out 3x/week to start eventually working up to 6x/week. Doing the workout consistently really helped increase my fitness level quickly and within two months I was doing the complete 4 miles. It's a nice tape in that Leslie breaks down the workout by miles--she'll tell you when you've completed 1, 2 and 3 miles, so if you want a shorter or less intense workout you can stop there (always cool down first!). The movements in the workout include marching (she'll call it walking), knee-ups, kicks, single and double side-steps and hamstring curls. They can each be modified for lower or greater intensity. She adds a little upper-body movement that you can easily leave out if you're too winded; or you can add hand weights to increase intensity if you'd like. Leslie Sansone has lots of different WATP workouts, some with weighted balls, ab-belts and resistance bands if those are of interest. I only have the one I mentioned above. WATP really allowed me to work at my own level of fitness (which when I began was practically non-existent), and within 4 months I had moved up to The FIRM videos. On some of the fitness boards I read, there are people who complain about Leslie's personality--she's *very* chatty, always smiling and very happy and positive. I always found her "chattiness" to be very motivating and sincere.
I think WATP would be wonderful for your mom. She can gauge it to her own abilities now and can grow with it as she gets stronger. Make sure you take a good look at all of Leslie's tapes to find the one you believe would be the best, taking into consideration any equipment that may be needed. Her older workouts can look a little dated (I just checked my tape and it's dated 2003--it's got very nice production values) and some of the titles are very similar, so check to make sure you're getting what you really want!
I hope this helps, and if you have any other questions, feel free to ask! Good luck to your mom!