I have always found that they hit between 900-1200 gms they stop for a while. That sexually maturity moment some sooner some later but I find they all do it. Some stop for a few weeks some a few months. It is just part of the natural cycle. Weigh her and keep everything correct and she will start sooner or later.

I would not change her diet they often don't do well with change. You may end up with a mouse eating royal and then need to switch her back.

I have a pet idea so i'll mention it. I have noticed with my collection they often go off food during winter leading up to breeding season. I have noticed that if the humidity starts to go up and sit in the high 60s low 70s for a few months mine start again. (breeding in wild populations is linked to some environmental trigger as they all lay at almost the same time.)
I have never read what that trigger is but it is set to align with the wet season so perhaps increased RH may signal an end to the season. It is just a guess on my part. I have not been trying this for long enough to say it works but this one time (this year) they all started again with in the same month and weeks sooner than last few years.