I don't think I read any of the Switzerland ones except Problem when I was a teen, and that's when Joey really starts being cringy imo. Although whether that's because I cringe because the triplets are teens and her behaviour becomes more inappropriate or her behaviour just is worse I'm not sure.
Problem she's fairly distant for the later books though. When ML comes to ask for help with Joan it's actually Jack who gives it, so that dilutes Joey for that book.
ML I have mixed feeling about.
The first book I really like her. She's a fun kid, and, unlike Joey, I think you can see the beginnings of her as she gets older.
I like that she'll talk to anyone, always makes sure people are included as much as possible.
I know people who would talk to everyone the same way-although ime at school that always had some teachers on their dignity. I do think that's a sign of not being quite "normal".
Following on from that, I dislike that everyone goes "only ML" and loves her for it. Reality is that, as with any strong personality, she would have people who hated her. the only one we have is Phil Craven, who clearly is a baddie (she likes maths, which is always the sign of a bad character in EBD's world!) and who disappears before ML has really got going.
And other than she's a strong personality, you don't see why she's so popular. You can see why young Joey is popular, but ML you are told she's popular.
I dislike the Gang. I see them what we used to call the "in-crowd". It's often people's reaction to them that I dislike though. There's one point they're splitting the form into groups and the teacher is "oh we must keep the gang together" and then splits the other friendships up. How to make a trip out miserable for the non-gang members.
I find her quite, I'm going to use the term "snobbish", about knowing Joey. Perhaps more like a name dropper. "Well Aunty Joey says, you know Josephine Betttany the author, she let's me call her aunty..." and imo she uses the "special relationship" to get away with more.
I think I wouldn't have wanted to be in her form ultimately because I'd have been too boring for her gang and everyone else is just fitted in round the gang in that form. She might look out in some ways for the others in the form, but actually the quiet ones in the corner wishing they could be asked occasionally to join the gang-she was into solving the large ostentatious issues.
Possibly that's unfair, but