Ok so there are two different threads on this subject for you but since im addressing diet I guess I will post here
Anyways yes Ranitidine is AWESOME!!! If you have a costco or something of that nature around you you can actually get it WAY cheaper than walmart because its 290 pills for I think 5 bucks or something but its works great EVERYTIME. I have a filly who will develope ulcers at the drop of a hat and she is a worrier just like your girl (warmblood but her mama was a ottb) and honestly whenever I notice ANY ulcer signs I do a week or so of ranitidine and it cleans everything up. We do a whole months course if she hasn't been on her you guard in awhile though.
Once the ulcers clear I would definitely suggest uguard or maybe even some smartgut pellets as a daily supplement to help ward off further developement. Remember ulcers can develope in as little as 3 days so keeping up her maintaince is key.
As far as diet goes lots of alfalfa or alfalfa pellets. Alfalfa naturally helps to treat and manage ulcers so the more alfalfa hay you put in front of her the better. Also cut back on the grains as sugar can irritate the stomach lining and leave your mare more suseptable to ulcers in the future. Lots of beet pulp and alfalfa pellets and if you have to feed grains I always suggest senior grains. Any horse can be fed senior grains and they have a lot of bran mash and what not in them so its easier to break down and digest.
Just a side note I know it sounds weird but what type of wormers do you use? I found that my filly was developing ulcers after wormings when I used any sort of moxidectin based wormers like quest. It seems to be too abrasive for my filly's digestive tract. I switched to ivermectins and pyrantel pamoate based wormers and we haven't had a ulcer incident in months.
Anyways good luck with your girl!!