Just wanted to update on this situation: the last two weekends I have showered and changed clothing (leaving contaminated clothing outside of the house) before coming near my daughter, unfortunately with no improvement. Both weeks we still had the same intense behavioral and physical symptoms from monday night through tuesday evening. Was really hoping this would make a difference! It really does seem as though my breastmilk is somehow becoming contaminated just by my being in such a glutinous environment. A mask is not an option for me as I work customer service and much of my job entails making a favorable impression on customers and speaking on a phone. So now? Either 100% wean from breastfeeding or quit my job.
I recommend continuing with breastfeeding. This is going to help her gut more than anything. Plus, she'll be miserable with the weaning (as will you). Doing so abruptly is bad for her health (stress, less healthy gut, greater risk of illness, etc.) and yours (future health, your stress, and, more immediately, mastitis).
I would recommend doing what the PP said about taking a day off to see. It might not be this at all. There could be something else bothering her--maybe you drink coffee there and there is gluten contamination? Maybe just eating on the tables there, using their refrigerators for your food, using the water? Maybe you touch your face without being aware of it? Doubtful in food prep, but still something that could happen accidentally. Perhaps it is from gluten, but perhaps it's from taking frozen breastmilk when you're not there? (Could it be contaminated with gluten--frozen before?) Can you give her probiotics, too?
With our DS1, we thought everything bothered him--but never could pin it down. Dairy can cause reactions. (Again, are you drinking coffee there with cream or milk?) Anyway, DS1 would projectile vomit (breastmilk only) about once a week, and had eczema--that was sometimes much worse than other times. We never really thought about gluten as being the overall cause until he was older. The GI feels that breastfeeding him for as long as I did was the best thing for him. (Even my mom, who was a naysayer at the time--it was a long time!--said that he really "needed" it as his stomach was is pain, and because he wasn't getting the nutrients elsewhere.)
This sounds like it must be a very stressful time! As difficult as it is to see your daughter in pain, even with the pain and the fussing, she's still getting such a great thing from you in the breastmilk. Even if you keep your job and continue nursing, it's still better for her to be nursing, even with a day that is less comfortable than the other days. I am confident that you'll figure out what is bothering her--and, it still may be coincidence. Again, even if you remain on the job, I recommend to keep nursing. It sounds like she's doing great six days a week!