Gender agreement of examples

Question

I don’t understand why  “Je me suis bien amusée.” adds the “e” for the feminine subject but “Je me suis lavé les dents.” does not when both speakers are female.

Answer

It's been a while. Does no one know the answer?

Answer

It's because there is a direct object "les dents". This question has been asked a lot, but so far the lessons have not been updated to explain this. Look at the answer to Gabrielle's question at the end of the Q&A here:

Agreeing past participle with subject's gender and number with (+ être) verbs in the compound past in French (Le Passé Composé)

Answer

Thanks so much for pointing me to the answer, Alan. I understand now but it's getting complicated! :) It would surely help if they'd add a note about it to both those lessons. I did read through all the questions on the lesson I asked about and didn't see an answer there. It should really be part of the lesson, or have a link to a lesson discussing it.