BACKSTORY:
This issue is between my housemate and I; let’s call her Mary. We’ve lived together for a bit over a year and when I first moved in we became best friends immediately. However with that closeness came disparity and we’ve had a few arguments since then. I’ve never had this kind of dynamic with any friend or housemate before, and the first time we fought was a shock to me. 

This particular incident has some backstory that informs my feelings and reaction. A few months ago we had a fight after Mary accidentally got the impression that I showered twice a day every day. She told me that I shouldn't; I said that I didn't except in special cases, but "also hygiene is a really personal thing and on really sweaty summer days I might shower twice, and I don’t think that’s unusual or a bad habit." She didn't take this well, citing how much water one shower uses and "to be asked not to take 2 showers a day in a share house is a reasonable request. What’s not reasonable is how self-righteous you are about it and how you’re trying to infer that your hygiene is being policed. Please don’t manipulate the conversation this way ever again, I don’t take lightly to manipulation whether it’s conscious or not." These were literally her words in the message she sent me.

I was actually really hurt by her reply. I’ve tried to take the criticism in stride and work on being less defensive and more clear in my communication. As a result of this conversation I have been extra careful to never shower twice a day unless I have a good reason.

NOW: 
I work night shifts and on this night got home around 10.30pm. While at work I had started to feel itchy and even after leaving the office it didn’t go away. While Mary and our other housemate John watched a movie, I laid in bed feeling itchy, depressed (for other reasons), and apathetic. After the movie John took a shower which gave me the idea to do so myself, as it might help my itchiness. 

Mary often has to be up early (earlier than the rest of us) and has asked us not to make noise once she goes to bed on school nights (including not flushing the toilet or taking showers, as our pipes rattle hard). I respect this and do my best not to make noise on those nights. At this point however Mary was still pottering around in the kitchen. At 11.40 as I got into the shower I heard Q grumbling about us showering close to midnight. I was in and out of the shower within five minutes and went straight to be afterwards.

The next morning I woke up to these messages:

&gt;HER: Hey showerinpeacepls quick question, why?
&gt;You got home an hour ago and tomorrow is your day off: why now?

These messages made me really uncomfortable. I feel like a child being asked to explain myself to my mother, except that I’m 30. I want to tell her what I’m feeling but I'm not confident I can face her without being sure: am I the asshole?