Holy crap! Glad she's fine. Sure looks like she ate something that stung. Spider maybe?
Okay, SHE IS COMPLETELY FINE NOW. This happened last night, she had a reaction to something (she wasn't stung or bitten). Her breathing was fine and her temperature was normal, I'll spoiler it just because it looks a bit harsh but she's okay now.
Teeth and gums look fine? Dental stuff can also cause crazy reactions.
Happy New Year from Peaches.