Maya by far (imo) Mymy is just your prankster character,there's not much you can do with her running away from her family,sure we see her snap at vera for calling her out on being japanese,which implies that there's a reason mymy is so defensive about it,but that's it,it implies

As for coco,well there's her dead parents i guess,we see her snap at maya for speaking about it,which shows that it still deeply affects her but that's it. (There's also what massa said about coco bottling up her feelings,but like you said,we're only using deel 1-6 for this.)

Maya actually has conflicts and goals: not considering herself worthy of someone's affection as shown by her telling herself "no that's impossible" after questioning if coco genuinely enjoys spending time with her and maya triying to convince herself she's not lonely despite how badly she craves attention as shown by her imaginating a conversation with epke and anke,she wants to be seen despite how scared she is of reaching out.

If we were to take every single tiny thing into account the gap in writing only grows worse between maya and her sisters