One hour of out-of-cell time per day is a recognized minimum standard for inmates in restricted housing, and the facility has an obligation to provide it. It is not a privilege that can simply be withheld without documented justification.
From the inside, the most important step is for your friend to file a grievance through the facility's formal grievance process, in writing, documenting each day that rec time was denied with the date and what happened. That creates a paper trail. Without documentation, complaints tend to go nowhere. With a documented pattern, there is something concrete to point to.
From the outside, your options are limited but not zero. You can contact the facility's administrative office directly, ask to speak with the warden or deputy warden, and raise the concern calmly and specifically. Identifying the written policy entitling her to rec time strengthens the conversation. Tennessee also has an Office of Inspector General that handles complaints about TDOC facilities, and a formal complaint filed there carries more institutional weight than a phone call.
If the denial is ongoing and the internal channels produce nothing, contacting the ACLU of Tennessee's prison rights project is worth doing. They handle systemic conditions of confinement issues and can evaluate whether legal intervention is warranted.
As for the concern that raising this might make things worse, that risk is real and worth calculating. How your friend raises the issue internally matters. A formal written grievance through proper channels is typically safer than a confrontational approach. Document everything and take the formal route.