It seems benadryl is the winner for recomendations here. I would probably do topical treatmeent during the day and oral at bedtime so you don't have a little zombie on your hands. Also, stick with the clear benedryl liquid if you can, I had a child get jiggy from the pink food dye once, not fun.
I would look into GSE(grapefruit seed extract)from the health food store. It "nukes the toxins" in your system and that might be what's bombarded your daughter's system. Also, vit c is a natural antihystamine. I used powder ester c when my kids where little, and titrated the dase to their age. Too much vit c can have a laxative effect. I used topical tea trea oil lotions-smells a little funky but worked well-if you wanted to alternate the benadryl lotions.
When my daughter came home from Girl Scout camping she was riddled with noseem bites=looked like she had chicken pox. We were going to disney to meet my sister and I just dosed her up with the above and put her in the car. Also I did oatmeal baths a couple of times. She healed up very fast that time when usually I hadn't been so agressive before over a few. I didn't want her to feel miserable in the heat of the day while she was with her cousins. I also take GSE when I get a fire ant bite because I swell up so horribly on my extremities. I also try and soak the bite right away in hot hot water as this supposedly neutralizes the venom from those bugs(I had used ice for years and it would not help)
HTH, LaurieK