I moved into this flat-share last year, we are four in total. People came and left during these following incidents, but the one I'm talking about and I didn't move. My flatmate and I are both university students (she's a lot older than I am). We were quite close to each other in the beginning, right when I moved in. However, things took a nose dive when the school semester started - she misinterpreted my words multiple times subsequently, as I'm not a native speaker.
The first conflict was about me saying "I don't know" in response to her assertion of an origin of a song, instead of saying "I didn't know". She took this as a sign of me doubting her and stopped talking to me angrily.
The second time was she asking me "is wearing headphones all the time impolite?", to which I said "it's okay, for me the most important thing is to say hi in the morning". I thought I had stated my boundaries of the least human interaction, but she took that as an accusation of not saying hi in the morning. She proceeded to say hi to me coldly from that day on.
The last attempt that I had with her was me trying to make things okay. I asked her if I did anything wrong, and if there are things that I can improve. Instead of an open discussion, she told me coldly, "we're not a couple, just get on with life". I was left helpless, living with someone who doesn't want to communicate.
She had complained in the past that she has a problem with the Wi-Fi connection, which I think is a result of a weak signal, as my connection suffers the same issue. I then bought a new router for the whole flat to share, however, she didn't buy that, sent me a message "There are too many waves, please unplug your router" and proceeded to unplug it. I agree that it wasn't nice to not inform her before the purchase, yet I just want to fix a problem that both of us have, with my own money! Furthermore, I understand that there are electro-sensitive people (let's not debate them here for now). What I am sure of is that she isn't one, she uses the induction plate and microwave just fine, both of these emit waves magnitudes more intense than a Wi-Fi router.
She blames me for not telling her before the purchase, but somehow she has quite some posters and plants in the flat without informing us, I'm not a fan of her double standard at all. To this point, I feel like she's targeting me - We have another flatmate who moved in just before this incident, he has a Raspberry Pi connected to the router, yet she didn't say a thing.
To be precise, I need to have a good Wi-Fi signal, I wish we can find a better solution than what is done now. How can I achieve this? Secondly, when she's stepping on my toes, I want to be able to stand my ground with open communication; and when I do something that bothers her, she does the same. Right now our communication style is "no talking, no harm" and I feel like I'm living in a library. I want to put an end to this, how can I achieve this?