The coach gun would work just fine for her in Ontario black bear country.
One point about light 20's is to be selective about what loads you put in them. There are a lot of stout loads on the market that would make it kick harder and sharper than a twelve.
I made some calculations for my 6.8lb 20 gauge double that I'll share:
>>>20ga. slug comparison:
-Challenger 2.75 mag, 7/8oz Gualandi DGS slug. 26.3ft.lbs recoil. 398gr@1610fps. 2291 ft.lb ME.
-Rottweil Exact 2.75” no.2317053, 7/8oz Gualandi DGS slug. 19.7ft.lbs recoil. 398gr@1361fps. 1637ft.lb ME.
-Rottweil Exact 3” mag no.2317054, 7/8oz Gualandi DGS slug. 23.1ft.lbs recoil. 398gr@1492fps. 1967ft.lb ME.
-Remington Slugger 2.75”, 5/8oz foster slug. 12.5ft.lb recoil. 273gr@1580fps. 1513ft.lb ME.
I would lean heavily toward the lighter loads with the Gualandi DGS slug, like the first Rottweil one in the chart. That slug will have much better penetration than the foster. Rottweil is a bit harder to find, but I got some at Triggers & Bows last year and have seen them elsewhere. Otherwise, compare the Challenger's with the 5/8oz foster. It's better that she doesn't end up despising the gun in the end. Don't think about it from a "facing down a bear" perspective, but more of a "developing a flinch while familiarizing one's self" one.
For bird shot, I calculated:
-Remington Game loads 7/8oz@1225fps 15.3 ft.lbs
-Winchester Super-X heavy game load 1oz@1165fps 18.2 ft.lbs
-Winchester Super-X "high brass" heavy game load 1oz@1220fps 21.4 ft.lbs
-Remington Nitro-Magnum 1-1/8oz@1175fps 22.9 ft.lbs
-Federal Prairie Storm 1oz@1350fps 30.9 ft.lbs!!!
As you can see, the variation can double the recoil! If you stick to the plain 7/8oz standard velocity load, I guarantee the grouse won't notice the difference. You really want to keep that recoil down. In my opinion, it really has to be justified to go over 20 ft.lbs in a practice or hunting load.
Note that an autoloader will have less felt recoil. There are complexities added here though. I could have recommended a nice SKB 20-gauge on the EE a few months ago... but a suitable one would pop up from time to time. If she's not serious about shooting though, I'd stick with the coach gun.
Also, make sure it fits her. If you have to cut down the stock, do it. When you do, put a good recoil pad on.
Good luck, I hope she likes it.