I try to keep up w the rosacea research and use rosacea.org site, and you have motivated me to do that again. Gluten sensitivity? Interesting.
When we were both first diagnosed with rosacea, we eliminated all the foods on the trigger list, then added them back, one at a time. The most surprising—and the worst trigger for both of us—is spinach!!! Some lists do not even include it. Your mom might want to try eliminating that, if she eats it. FYI, kale is okay and an easy substitute.
Others for both of us are citrus fruits (no lemon in our water; no fruit trees in our yard) and hot spices. The following can aggravate it, but we can both eat these occasionally (not 2 days in a row): tomato sauce, avocados, bananas, yogurt. He does not like the last three, so that is pretty easy. For some people, caffeine and/or two much caffeine at once can trigger flareups.
An interesting, and I find, useful, nutritional source is the zone diet by Dr Barry Sears (zonediet.com). His theory that all foods react or are processed as hormones by our bodies makes sense to me. Thus, whenever you eat, you should seek a balance of carbs, protein, and fat (40%40%30%). Too much protein makes you buzzy(mean?). Too many carbs make you sluggish. So you start noticing how balanced you feel (in the zone) after a meal. And you should not go longer than 5 hours without eating something is true for my body. Years (decades) ago, I bought some of his products, but I am now pescatarian, so I do not think I need a fish oil supplement, and I eat lots of fruit and vegetables, so I do not think I need the polyphenols. The portions of carbs are a bit restrictive, but Dr Sears says you can achieve the benefits of “the zone” if you stay in the zone at least 80% of the time. His info on the web site is all free.