I had one for about a year that eventual resolved itself. I practically lived under hot compresses for several months. They may have kept it from getting worse, but there's no way to know.
I did use a combination of antiviral herbs (you can google that term for info) for a couple of months before it went away. I don't know whether they helped, either, but it did eventually leave. Unfortunately, pretty unpalatable and probably not advisable for littles. But google 'antiviral herbs' to see whether any might work into her diet. Or possibly add a little to honey, my new go-to remedy that seems to help just about everything.
So, recently, I've added manuka honey to my medicine chest. It has multiple antibacterial, antiviral, and antifungal actions when applied topically (NOT on the eye, of course) and/or internally. My daughter, who is in medical sales, turned me on to this amazing product, which helps with all sorts of small wounds, infections (including uti), rashes and burns. I've been astonished by the effectiveness of the brand I've used, MediHoney. It's completely sterilized to be free of botulinum or other microbes, so presumably is safe even for babies, though I'd check with a doctor first. You can find some brands in health-food stores, but check for sterility.
I sure hope you find a solution. I'd love to hear about what works.