why is my dog playing emotional ping-pong?

My 9-year-old pup had an accident on my boyfriend's bed yesterday, and now she's switching between happy tail wags and total fear mode! One minute she's cuddling under blankets, the next she's cowering like she's in big trouble. She's eating normally but keeps hiding in the bathroom or his dog bed. No signs of pain when touched. Has anyone's dog ever held a guilt-grudge this long? 😩 #confusedpetparent #dogbehavior #seniorpup #petguilt #Pets