Megan obviously came! And flailed with joy. She would have been super touched at the effort put forth to celebrate her birthday and thanked everyone involved/the came profusely for it. Truthfully, she probably would've gotten a little teary because it being her first birthday celebrated without her parents and her brother not being there, but she would have squashed it and had a good time. Ernie got a million, billion hugs and Salazar became her go to person to return to every time she wandered off on her own. She would have drank a bit much in the spirit of enjoying the party and then clung to her boyfriend because he's good for that and stuff.
Harry and Dennis both came as well and mingled a bit.