Stand her on a table so you don't have to hold her. While she's on the table, pull her to your body, drape one arm over her and lock her in with your elbow, this frees up the hand on the draped arm and you have a free hand/arm too. Alternatively, swaddle her in a towel to capture her wings, then you should be able to handle her more easily.I can’t keep her mouth open long while holding her. I will check her again in the morning and see if it smells yet and see how it’s progressing.
I agree, it looks like it might be Canker but with no odor, it may be something else.
Is there a pocket of that material under her tongue too?