Catherine is 2"-3" taller than Heather and has several llbs advantage too and I reckon that Heather would get badly beaten in this one. Heather is a fiesty lady but in several TV shows she has been shown to be unable to back up her aggressive characters with equal physical presenced. She is not frightened to get in a fight but she always seems to come out of it worst. Even when her rivals are prim little good girls like Emma Samms she ends up taking a beating from them. Heather talks a good fight and is aggressive enough, but when it comes down to it she lacks strength and other girls are quick to take advantage.
What you say about their physical difference is true. However you are not correct in your description of her fights. Of course they are all staged and she has lost some. Specifically I think she won that fight against Emma Samms in Dynasty. If I recall correctly they feel into the mud and Heather was clearly outfighting Emma. But it didn't go to conclusions as they started giggling and ended up friendly. Heather has slender legs but if you ever watched
The Battle of the Network Stars you would have seen she was very athletic, very competitive, and perhaps the fastest sprinter of all the women. Now Catherine also competed in a real competitive show that I can't remember the name. It had to do with city girls competing with country girls. She completely dominated Cindy Garvey horse riding fight (on the shoulders of some guys). She easily bent Cindy completely backward. Cindy's flexibility and small frame kept her from falling off for a long time but the final result was inevitable. Perhaps Catherine's size gives her an advantage but don't underestimate the size of the fight in the dog of the real Heather.