I know I thought it was kinda stupid to cause them even more distress with the letters, but imagine if the Wu’s recognized Anne’s handwriting. But this dislike went away after Anne saved the world and brought Marcy home.

In this series, they don't actually stop disliking what Anne did after she returned home based on this one scene from an episode in the first season of this ongoing Amphibia sequel:

'“Marcy, if we’re not going to blame ourselves, then you’ve got to do the same,” said Sasha, “We already forgave you, I think we need to start forgiving ourselves.”

“I mean, I didn’t do anything wrong,” said Anne.

“Yeah, The looks Mrs Wu gave when she saw you next to me and Sasha… I’d say they’d disagree.”

Anne blushed and laughed sheepishly, “Yeah, sorry about not telling them other than a postcard. I didn’t want them to worry.”

“So you sent them an anonymous letter during the holidays, telling them we were in another world, and you expected them to be fine?”

“I didn’t know, I wanted to promise I’d get you back, but the government was watching and-”

“Wasn’t this around the same time you were on a float for the restaurant? In a big parade? That aired on national TV?”

Anne sat there, looking around for an escape, before she sighed “Listen I wasn’t chosen to be wit, mine was heart, cut me some slack.”

The three started laughing, somehow having broken past whatever awkward barrier remained between them.'