Can you try to get the thread cut all the way? Has she swallowed part of it? This is a common problem with strings, thread, or hairs. They can be eaten, and after wrapping around the tongue may go down the throat and cut off circulation to the tongue. If the thread is cut in two, the tongue...
Canker is yellow and is a parasitic infection carried by pigeons and wild birds. It can be treated with Aqua Zole (metronidazole.) I would try to make sure that she doesn’t have a hair or string wrapped around her tongue causing swelling that looks like a lump. Here is some reading about canker...