Overprotective mom?

So im gonna start out with my age. Im 18. Its just me, my little brother and my mom. We live in some ghetto low income apartments which isn’t so bad at times. None of the apartments have laundry machines in them so we have to share a laundry room with the whole complex. I went to wash my towels today but they were all taken and one was broken but I noticed one was finished so I was just going to wait for the person to come clear it out. I waited and here comes a person to take out their things from the dryer and their folding it and taking their time while on the phone and I felt bad to interrupt but I had to ask if the washer was hers. I nicely asked “excuse me, is this your washer?” and she turned quickly with a mean face and sharply said “Yeah, I’ll get it out!”

It kinda scared me a bit because I didn’t mean to get her mad, I just wanted to know because I had been waiting and I needed to use it. My mom got home and I explained the situation and how it was weird because I don’t even talk to the woman and this is the 2rd or 3rd time she gets ugly with me. My mom got upset and went to confront her. Im a little embarrassed but Im glad I have a mom that will always be there for me, I just feel like she shouldn’t have confronted her... is this wrong or right?