Back to the buckets. 
If Sheila had had her menstrual accident during the day or early evening, would she really have put her blood-soaked undies in buckets in THE KITCHEN? Where people moved around and they could be knocked over - where people ate? A kitchen is a kitchen, a scullery a scullery, a laundry room a laundry room. All of those kinds of rooms were at the WHF, why the kitchen? Would June have allowed that?
What was Sheila wearing after the "accident" if it happened during the day?
1) We don't know the buckets were not moved to the kitchen by someone as the house was being cleaned up. We only know they were in the kitchen when Ann looked through them.
2) We don't know what their habits were. My mother used to soak our stained clothes in buckets in the kitchen because she would fill and empty the buckets in the sink before taking the clothes to the washing machine. She had no sink in the laundry room. If they were in the way when she was cooking she would move them somewhere else like the pantry.
We especially don't know what Sheila's habits were and not to knock the dead but WHF wasn't exactly the most cleanly place. There were all sorts of clothes all over the stairs and for all we know the buckets had been in there but were moved either to go up those stairs. police searching the house or someone who was cleaning out the house later on. It is hard to know whether june woudl have had an issue with the buckets soaking overnight in the kitchen or not. The people who would know best were dead and farm workers who might have a clue were never asked to our knowledge.
Since there were no tops that could have had GSR/blood spatter from the victims no one really cared about the buckets and only Ann bothered to mention them because she rattled on and on about pretty much everything. I don't think it is going out on a limb to assume she was a gossiper.
I don't have a sink in my laundrey room either. My wife soaks clothing for a little while in the kitchen sink sometimes but usually in the bathroom. She will have panties hanging around the tub and buckets with other things soaking and it is always a pain to take a shower because I have to move things. OK correction her clothes soak in the master bathroom. Other clothes that end up stained are soaked downstairs in the kitchen or if soaking long term than outside. She also will put clothes on the deck to dry either over the railing or on the floor even. We have a large clothesline she made me install (the kind with a post) but she rarely uses it. I stopped trying to figure out women and their laundry habits.