Don't forget Lilo's teacher, I painfully relate to Lilo being the "weird girl" so I understand where she's coming from when she got angry at Myrtle for calling her "crazy," I feel like a lot of kids growing up who were considered strange while dealing with a hectic environment have at least once had an outburst like this.
Her teacher is another mentor figure in her life that wants the best for her except he's an outsider looking in so sometimes he doesn't fully understand Lilo's thought process, all he can do is listen and attempt to steer her in the right direction. That's only in the first movie, there's to his relationship with Lilo in the cartoon and the direct to DVD sequel but I'll be focusing on the sequel since that's where it shines the most. (Also there's a debate on whether the cartoon is considered canon or not, personally I think it is and that the sequel takes place a few years after the finale)
The sequel has a big theme around family and since Lilo doesn't have a mom she feels left out when Myrtle's gang starts talking about how their moms can help them with their assignment (they mention it right in front of her too which still angers me so much) upon seeing this her teacher inspires her by telling her about her mom winning the competition and how graceful of a performer she was, he's a lot better at the mentor role in the sequel than he is in the first imo.
Lilo & Stitch is a great example of a story that has no villains. It has antagonists, sure, but most of them are well-meaning. The worst person in the film is that little shit Myrtle, but she’s not in the film that much anyway.