Despite My Melody and Kuromi's rivalry on how it was portrayed in "Onegai My Melody", you can tell that they were NOT the best of friends... Especially Kuromi hating My Melody for some reasons. However, their they became friends and the two had some changes on how they were portrayed in the SCA series. My Melody was less clumsy and naive and more of this very cheerful kind of girl, and as for Kuromi, her rivalry role was really tone-downed so she can no longer have this strong hatred for My Melody anymore. As to why I think of that is because it's likely the fact that SCA is an AU as all the characters live on their own (with their houses of their very own) and have their own places to run like gift shops, bakeries, and more. Even they all live in the same exact town (AKA Sanrio Town) that isn't too far from each other! Yep, that also means that Kuromi and My Melody no longer live at Mariland for this series.
I know, I know... I had to get that out of the way first before I can finally talk about Dot and Helen here. Speaking of Dot and Helen, I think they can work as friends... Especially since Avenger era Helen is older than her so Dot doesn't have to instantly compare Helen's "cuteness" to her right away. And Helen's into some girly stuff like Dot would be like fashion and whatnot. Plus, they're into handsome-looking guys as Helen tends to possibly think Chuck E. is handsome.
Okay, another example out of the way and here's the template if you wanna use it for yourself:
