I (25) live with a flatmate (22F). She is a nice person in general, even if she has a lot more energy than me.
The problem is, she tend to take her showers really late into the night, and I have insomnia, so it wakes me up and I can'tgo back to sleep for a few hours. The bathroom and my room share a wall, so I hear everything really loudly. She knows that, and I always warn her when I'll be trying to sleep so she can go take her shower if she hasn't already (usually I tried to go to sleep at 10pm, which is already pretty late for me).
Recently she stopped taking her showers after I told her I was going to sleep (even if she still makes a lot of noise in the appartement to the point I have to sleep with earplugs), but she started taking them early in the morning, especially the only week where I can sleep late. It's frustrating, even more when I leave for school before her, meaning she could have taken her shower later and not wake me up.
And today I snapped. She casually told me that I look tired, and I responded with "If someone didn't wake me up all week when I could sleep a little more, I wouldn't be". Her bf took my side, but she started getting angry, saying she can't take a shower at 11pm before going to sleep, she couldn't take a shower at 7am when waking up and she now would have to stink all day because of me.
When I told her she could take a shower earlier, like 8pm, and not 30 minutes after I told her I was going to sleep, she got even more angry, saying that there was no point in doing that cause she was going to stink before going to bed.
At this point, she just took her plate and left the appartement to go eat outside cause her bf and I were arguing against her about that.
And it's where I might be the asshole? Should I just let her take showers a little late even if it bother me to sleep? Her bf seems to think like me that she completely disregard my feeling and my sleep because she can't work around a good schedule to take her showers at normal hours, but I don't know if I'm being too harsh on it. She is a good friend and I don't want us to be in cold just because of that.