When Power Is Never Enough Or Far Too Much...
She shoots in a small space. She wants to do work at a wide aperture - wider than f:4. Even with one single light from her 400 w/s set and her camera set to a very low ISO, she still has too much light for the subjects.
She's tried the temporary dodge of covering the front of a softbox with a grey chiffon, but this contributes an unwanted colour cast. Basically she just has too much light.
Tempting to trade it in and get lower power, but she may have larger premises one day or be taking photos of big groups out in big halls...so keeping the power is good too.
The best solution would seem to be the Lee company and their theatrical gel material. It comes in large rolls and can be had with either clear colours or clear grey or translucent finish to drop even more light.
I hope she tries it and can report results. There are a lot of people who might be in her predicament - if the Lee material works I'll report it on this blog.
Note: I shoot studio too, but sometimes need to have all the power I can get for tiny apertures. Different subjects, different vision.