Here is Most of What You Need to Know About Ulcers
That being said, one of my close friends had to take antibiotics (not sure which one) for an infection (not ulcer related at all) and the antibiotic, itself, pretty much wiped out the healthy flora and fauna in her digestive system. I’m guessing that when that happens, you can become susceptible to ulcers, because all of the protective bacteria is destroyed.
From the above article, it seems like hpylori bacterium is the main cause of ulcers, and next is a genetic tendency towards ulcers, and certain meds, especially certain NSAIDS like aspirin, Naproxen, and Ibuprofen. Stress, itself, does not seem to cause ulcers, but it can exacerbate them, as can certain foods, and certain meds.
I hope she’s better soon : )