I've known girls who have used it. If you were on the forums in the earlier 2000's for about 5-10 years after, many used to post their protocols and stuff openly at times. Personally, for a very very large percentage of females, i'd say it just isn't a good option. However, if you are a top competitor, and you are in final weeks of prep, then it will definately make a difference. I agree with Kaladryn on this one, dosage and individual response will make all the difference. Microdosing can make a huge difference, though you really have to trust your source/chemist in being accurate on their final product.
After female bodybuilding took a hit, i haven't seen as many women post about using it (not saying it isn't still used). The crowd of women I knew on the forums 'back then,' have all pretty much retired...from competing and the boards.
If a female is not competing, or if the have great response as a lower level competitor, I feel the usual low HGH with the tried and trues of either Anavar, winstrol, primo, eq, and npp to a degree, will be best...and based of their own response and trials. Obviously, if you need higher doses as a female at a lower level of competitiveness, it might be better to just throw in the towel imo, unless you don't mind the sides.
But to answer the question directly...there were many females whom used tren back in the day at very low doses. I think some used 'moderate' doses...but good luck finding any of this online these days.
I can't speak for modern day competitors...or everybody