That makes no sense. How is it not the performer's choice?
The studios can't release that which hasn't been filmed. Some actresses do choose to overwork themselves and release 3 to 5 titles per month, it's just a matter of how many days are they willing to schedule per month.
A performer has no say about how many movies are released or when , that's up to the producer , it is the producer who decides whether he'd publish two movies per week or only one , Moodyz already released 7 movies with Yui Nagase plus one or two VR issues ,apparently everybody is issuing all he has about her as soon as he could. Yes she may have shot lots and lots of scenes she's been hired a lot , would have been stupid to refuse ,she didn't know whether she'd have any success or not thus she grabbed all the money she could get, but they're not meant to be released all at once , a wise producer shelves some and issues them at a steady pace.
Nobody wants to burn out an actress with potential success, but they want to shoot her as much as possible at the lower possible wage to increase their earnings when she'll get popular and has to be paid much more.
My bad, I didn't follow her so I wasn't aware of her exact release schedules. 2 is still really fine. When you compare with Akari Mitani, Touka Rinne, or other "popular" girls, they will probably not stay in the business for few years. Aki Sasaki is a good example.
Maybe the girls say that they want to shoot as much as possible to leave the industry quickly after making as much money they can by doing everything. Nagase Yui seems to be a freelancer, so she choose what kind of movie she wants to do. When a girl is a contract girl (let's say with S1), they do the same movies as the other girls there.
Another thing is that an actress loses her "value" as time passes. If she doesn't attract fans (not beautiful enough, unskilled, ...) she has to do more hardcore stuff to get more money (or at least the same amount as when she started). There is a reason if actresses Julia, Yui Hatano, Ai Sayaka and some other actresses never had to cross that line to stay popular.
A girl can't be sure she'll become popular , she certainly hopes that, but she doesn't actually know so she tried to get as much money as she can, otherwise she might shoot as you say once a month but with fewer issues and obviously much less money, besides producer and directors may not want to wait until she gets popular and have to pay her a lot more per movie
So aside maybe her debut movie an actress is not paid that much when she begins , or better yet she's paid much more when she succeed and is in demand to a point to shoot just one movie per month and still make a living out of it.
Beginners don't have such luxury, if they don't succeed they won't be hired that much and certainly not paid as much as a successful actress
Talking about popular actresses , Elli Akira/Yuka Osawa did pretty much everything from the very beginning of her career :anal, bukkake, double penetrations , pissing, enema , uncensored all within a couple or maybe three months after her debut , worked really a lot , still she become quite popular , for her come back this year she did three movies already as you suggested she might want to pace her return , but those who own her movies thought differently all three of them will be issued in a week , just a week and then nothing , no issues scheduled for October.
So the actresses have no control with the publication of their work it's all up to the marketing strategies of their producers