What is "canon"?
Do you mean what is canon on the show? Or what does the word “canon” actually mean?
Canon refers to things that are confirmed and verifiable within the body of a work. So like, Snape kills Dumbledore is canon. Hermione has a crush on Harry is fan theory or headcanon. Things people actually say or do are canon within that work. Things that are inferred or theorized are not canon.
Riley telling Maya she’s her extraordinary relationship is canon. Riley and Maya saying they love each other is canon. Maya holding Riley in her lap, stroking her hair, and softly singing to calm her down is canon. Riley and Maya holding hands all the time like it’s the most natural thing in the world for them is canon. Riley and Maya frequently gazing into each other’s eyes is canon. Maya looking at Riley’s lips is canon. Maya biting her lip while looking at Riley is canon. Riley getting the two of them matching Claddagh rings as a birthday present for Maya is canon. Riley and Maya saying the same things that Cory and Topanga say to each other is canon. Maya and Riley repeatedly telling each other that they will always be together is canon.
Riley and Maya having romantic feelings for each other is not (yet) established as canon.