Well, I am definitely not an expert, but I can tell you what worked, and didn't work, for me.
I was the first one (between my husband and I) to start riding, but he soon saw how much fun I was having and jumped on the bandwagon also.
Until the age of 47 I had no interest in motorcycles, then I met a co-worker about my age who was in to scooters. My interest was piqued, and hearing my uncle and girlfriend talk about his Buddy 150, and what a blast they had riding it (she has her own Buddy now

) got the ball rolling so to speak.
First, I went to the DMV, and took the written test so I could get my 90-day learner's permit.
I had the scooter delivered to our driveway, then rode it back and forth in the grass in our back yard several times (we're only talking 20 feet one way, then turn it around and back the other way 20 feet). Once I realized that it wasn't going to take off without me, I rode it across the street to the culdesac. After a time or two around there, I was ready to ride around the neighborhood.
The next weekend I got up fairly early and rode a couple miles away to some empty (well, closed for the weekend) business parks and rode there a bit...then on to less congested streets around town, building up bit by bit until I rode it to work one day (on the WEEKEND, when there was no traffic) which was a 10 mile one-way trip. I had signed up for the MSF course and as soon as I was able to take it (a few weeks out, unfortunately) I did, riding my own scooter in it.
I progressed from there, going a little faster and further, riding on a little busier streets only as I felt more comfortable. It took me quite a while to build up to going on the freeway (something that not everyone even wants to do, or should do...it really depends on your road speeds, conditions, weather,
the demeaner of other drivers, and of course your comfort level).
But back to the Buddy. I did finally get an MP3 250, after I'd had the Buddy for a couple of years and put a few thousand miles on it. I'm really glad I learned on the Buddy, as (for me) learning how to ride an MP3 with no prior scooter or motorcycle experience would have been a HUGE mistake. MP3s handle quite a bit differently than Buddys in some respects: center of gravity is much higher, heavier bike, takes more room to maneuver. My main issues, when I first got it was the higher center of gravity and learning to act with deliberation. Meaning that when I pulled up to a gas pump, I needed to lock the suspension, shut off the kill switch, turn the key off, pull up the emergency brake, then get off the scooter. Getting back on I was likewise careful to make sure the emergency brake wasn't on before taking off. If you "oops" on that, and give it gas, if your feet are up, over you will go. I never did that, but it was close a couple of times...you have to be very conscious about your actions. A biggie, is to not come to a stop in a hurry with your bike not level, as the higher center of gravity could make you drop the bike. I was lucky with that one too. Thanks to the Buddy I was used to coming to a smooth stop staying vertical.
My point here is
if she is interested, start her on your Buddy, and have her get totally comfortable on that (like months of comfort) before having her try the MP3. If she's ambivalent about riding, a fall may well turn the ambivalence to "no thanks!" The Buddy is SO easy to learn on, it just makes learning fun! I can't stress enough that everything has to be at her own pace and comfort level.
And of course the MSF course is a must! Much of the time they will let you bring your own bike which IMO only makes sense, if you already have the bike you want to ride.