Help with confronting my flatmate

Today my flatmate, for anonymity sake lets call her Susan, always has a go at me about the cleanness of the flat. Now I’m going to be honest, I’m not the cleanest flatmate around but I do my dishes, clean up after myself and sweep up if necessary etc etc so the flat looks presentable.
Before I left the flat in December to go home for Xmas (in line with govt Covid guidance!), I cleaned the flat before I went as anyone would do. However today (April 2021), my flatmate messaged me today saying that the flat was in a disgusting state and that it basically looked like it had not been cleaned.
Again, I’ll be honest. I did expect to be back in the flat in January so the clean I did in December was not a deep one but just a do-over till I got back around 3 weeks later. Obviously plans changed and here I am almost 5 months later not back in the flat.
I just feel like she’s making a fuss out of nothing or at least overreacting as of course the flat would get dirty if it hasn’t been cleaned in five months surely?
Another thing that annoys me more is that during our time in the flat prior to leaving, she has left unwashed plates etc on the side for two weeks or so and occasionally left mouldy food in containers to. If she was super clean I would understand but I feel her having a go at me for the cleanliness of the flat is somewhat a double standard.
I don’t know if I have a right to confront her or not or if to just leave it? Do I even have a right to confront her? What are your opinions on the matter?