I think that as Regina uses magic connected to the forest based on what we've seen so far, she's strong when fighting in the dense forest of Viridice/Lycalis, and also got a large boost in strength as she's fighting near the large magical tree in the capital. Outside of the forest, Regina probably isn't as strong.
Naya is a cat hybrid, and big cats are at their best in open plains/clearings when fighting or chasing, although they can sneak and ambush prey in forest areas (and we've seen Naya do that with poor MC). Naya is probably at her best when fighting in plains as there's greater freedom of movement than in a forest, and restraining her within said forest is likely her weakness, which Regina exploited.
Now I want to see Naya ambushing Kendra in the darkness of the forest for the lulz.