Treefrog, best advice you got was forget the 20 guage. Trap is a 12 guage sport and Mama won't break enough targets with the 20 to stay interested. It's always hard to guage if a new shooter really will shoot for any length of time but the BT-99 or Micro is a great start. So are the Rem, Baretta auto's but they are a little more complicated to operate and clean than break open guns.
My wife sarted with a Citori O/U choke tubed gun as she started playing with trap, and sporting clay's the same season. Same size gal as yours but mine started at 55. Citori has 26 inch barrels but also had a Soft-touch to eliminate recoil. She's won a trophy with it and carries it in the Dove field. Actually killed her limit one day with it.
Bottom line, either a semi-auto with a cut comb or a break open gun with a recoil reduction system and cut comb. With the advent of kid's and more Ladies entering and moving up or quitting, you can fit your lady and be able to recoup your money when she moves up or quits with what I've described above.