Define "official". I think it's official enough. It's true to the source content, anyway.

Strawberry always talks about Canola being her BFF, though Canola doesn't do the same in her secretary quotes. And Strawberry mentions idolizing Sakura and Mei in her intro and secretary quotes as well.

Strawberry and Canola do get together in chapter 13 of the main story, as well as one of Blossom Hill's nation defense maps.

https://www.youtube.com/watch?v=85mnDk1L-NQ

All four girls are in Strawberry's character quest too (which we still don't have even though it was one of the first ones released in DMM, grr).

https://www.youtube.com/watch?v=qiM9Y0VxnCw