Neosporin, polysporin, plain triple antibiotic ointment from any pharmacy. Always without the added pain killer ingredient, birds don't tolerate that well. I'm not familiar with the other recommended product. If it's like "liquid bandage" which seals (I don't know this one) then it could sting, or possibly seal in bacteria. If it's like that, then I would personally not recommend it. But again, I'm not familiar with it.
Hard to say why it happened, could have been something very momentary, and if blood was drawn that would attract others.
You may have to hold her to get her to eat, hand feed, or if she's really having trouble you may need to learn to tube feed. I will give a link with much info on that, and if you need more help PM that author who I believe will be willing to help you individually.
When you aren't able to be there, I have found that putting a rolled up bath towel around them, like they are sitting in the middle of it, helps keep them upright and more comfortable, and you can work it so it supports her head/neck in a more comfortable position. You can try that and put small open dishes of food (mash or dry, whatever works best, and a small dish of water within her reach (nothing she could drown in).
Best tube feeding video:
The link above requires a login, but I have the video saved to my drive and can email it if anyone wants it.
Two great threads on how to tube feed:
From Technical Procedures for the Avian Patient, by
Amy B. Johnson, CVT
Crop Feeding
Crop feeding is...