Frost, whose claim is now down to 3lb, has enjoyed a fantastic season so far, securing a Grade One victory aboard Black Corton at Kempton on Boxing Day, as well as drawing plaudits for a string of other high-profile victories.
The Ditcheat trainer said: "She rides very well. She has been given the opportunity to ride some very good horses and delivers when she needs to.
"She rides well and listens and is enthusiastic, but most of all the horses run for her. That's a big thing - they run and jump for her. There are a lot of good qualities in her and she seems a very good chase jockey.
"Horses run for her and run sweetly for her. She just wants minding a fraction, as there are some horses that are ideal and some that wouldn't be."
While Nicholls is full of praise for Frost's achievements to date, he feels the 25-1 offered by William Hill about the 22-year-old becoming champion in the next 10 years is not an overly-generous one.
He said: "You need to be riding six rides every day, like (Sir Anthony) McCoy, and dealing with the falls. I just think it will be impossible. I think it will be hard on the Flat for Josephine Gordon, but it is possible.
"I'm not saying it won't ever happen, as it probably will do one day, but I think, being realistic, she just has to be minded and looked after. If she starts having falls, that would be tough physically.
"Just because she has ridden 40 winners and is doing well doesn't mean she is going to be champion jockey.
"It would be nice if she proved me wrong, but what I am trying to get over is it would be tough to be in a situation like McCoy, riding all those winners and having those falls to deal with.
"What she does now, if she picks and chooses the right horses, she will have a great career and do really well. To be champion jockey, you have to be riding for everyone and anyone.
"You look what McCoy did and (Richard) Johnson does every day, all the travelling - you just have to question if that would be suitable for her. I was talking to her dad (Grand National-winning former jockey Jimmy Frost) and he was in 100 per cent agreement with me to carry on what she is doing and she will always do well.
"She is probably better off staying with us and riding for her dad. I think it would be tough for her to land a big job as a number one, but who knows? A small stable might like that, but I can't see it at a big stable in the near future."
Frost is one of an enviable selection of riders at Nicholls' disposal, with Sam Twiston-Davies currently in pole position at the powerhouse yard.
Nicholls said: "Obviously Sam is number one, but he has no retainer - that is why I let him off from time to time to ride for his dad (Nigel Twiston-Davies).
"Harry Cobden, Sean Bowen and Bryony ride a lot. Below Sam, there is no real pecking order.
"Any three of them could be number one as they are all very talented jockeys. Bryony is not far behind them, she perhaps just lacks that little bit of experience."
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