AITA for leaving a wet bath mat over the tub to dry?

Hi, I’m Lea (18F).

I recently got into a fight with my dad’s girlfriend’s mom, and I feel like I got ganged up on over something small.

My dad’s girlfriend is Abigail (30s F), and her mom is Sophia (60s F). I share a bathroom with Sophia. We each have our own side of the counter and separate sinks. We’ve had issues before with her moving my stuff, so I eventually got a shower caddy that sticks to the wall so my things wouldn’t be moved. That seemed to solve things until today.

I went into the bathroom to shave my legs. I don’t like showering to do it because I get cold, and I only need my legs wet. So I ran a shallow bath, just enough water to rinse my hair and wipe my legs with a towel. The bath mat was already draped over the tub, and I was going to use it to sit on while shaving.

Everything went fine. I cleaned up the hair, wiped down the tub, and put my razor and speaker away. I also put my towels in the laundry like I’m supposed to.

I noticed the tip of the bath mat got wet, probably from raising the water level briefly to rinse hair off the walls. Since it was damp, I left it draped over the tub to dry instead of putting it on the floor. I thought that made sense because after showers we’re supposed to hang it over the tub to dry anyway.

Later, Sophia sent a message in our family group chat (which includes her, Abigail, my dad, and Abigail’s grandma) with a picture of the bath mat over the tub and said:
“Lea? Why shower with bath mat in tub?”

I said, “It’s wet?”

She said it was “soaked” and asked how I got it so wet. I explained what happened and apologized if it bothered her. She replied, “My happiness doesn’t depend on a wet mat. Try harder.”

I felt embarrassed because this was in a group chat. I told her she could’ve talked to me in person and that “try harder” felt mean. She said she wasn’t being mean and that I needed to “try harder to be responsible when you share space with others.”

I tried explaining again that I shaved, cleaned the tub, and left the mat to dry because I thought that was correct. I said if there was a better solution, she could tell me instead of just saying “try harder.”

Then Abigail stepped in and said household communication needs to stay in the group chat. She also said if the mat was very wet, I should’ve wrung it out or put it in the washer and dryer. I said that would’ve been helpful to know instead of being told to try harder.

They both kept insisting it was my responsibility and that the better way was to wash and dry it. I felt like I was being treated like I did something horrible over a small mistake. Sophia later said she was being sarcastic when she said “try harder” in response to my “sorry if that doesn’t make you happy.”

I know I could’ve wrung out the mat or washed it now. But I didn’t know then.

AITA for how I handled this? What could I have done differently?