Post some pictures. If nothing else, I'm curious and like to learn. You might also want to think about tube feeding her if she is not eating and drinking.
This is what's in my AAAP Avian Disease Manual
D. TRICHOMONIASIS
(Canker in pigeons and doves; Frounce in falcons)
DEFINITION
Trichomoniasis is caused by
Trichomonas gallinae, a flagellated protozoan. Pathogenicity varies
greatly by strain. The disease is characterized by raised...
Is the pus all over the roof of her mouth or just the cleft?
Normal
This one has a sinus infection - You can see the pus in the cleft, but not anywhere else.
More on dosing:
From: http://www.harrisonsbirdfoods.com/avmed/cam/09_therapeutic_agents.pdf
(Chapter nine from here: http://www.harrisonsbirdfoods.com/avmed/cam.html)
About dosing... Some pigeon people give a whole 250mg tablet, some give the 100mg tablet. My vets told me to give 30mg/kg for 5 days when treating blackhead (histomoniasis), another vet said that I could give up to 60mg/kg, so do your research and weigh your bird!
I think you can give both at the same time. I know you can give Baytril and Metronidazole together, so I don't think that it would be any different with Tylan. Just remember that antibiotics kill good bacteria, too, so one does open the door for other bacterial and fungal infections when using...
You can also buy it in 100mg tablets:
http://www.ebay.com/itm/MedPet-Meditrich-100-tab-Treatment-Trichomonias-Pigeons-products-Raptors-/261151586912?pt=LH_DefaultDomain_0&hash=item3ccdd8fa60