AITA for snapping at my parents after they opened my mail?

Am I the asshole? I live with my mom and sister, neither of which respect my boundaries. I ordered barrettes a few days ago because I recently ran out and I need some for a cosmetology class, they came in this morning and before I had a chance to check my mail my mom brought my package inside (which I'm completely fine with and I usually would thank her for) but instead of putting it in my mail pile she opened it up and went through the package.

When I found out I asked why she would do such a thing and she claimed she "didn't know it was for me." I knew it was bullshit instantly. She always opens packages by cutting out the shipping label (which this package had my name on the label) and then before looking inside the package she cuts up the label.

I understand it was just some barrettes and nothing to be mad about but I have ordered some very private things (as people my age do) and I would be scolded by her if it was something she didn't approve of (including gauges, nose piercings, all the strict parent things). Ive told her before that she needs to respect my privacy and not go through my personal belongings anymore since I use my own money and I am at an age where I could move out but she just doesn't listen. She also refuses to let me move out so after having enough I finally snapped at her today and told her off about needing personal space. She just rolled her eyes and walked away and now I feel shitty. Am I the asshole?

EDIT: The way my mom is stopping me from moving out is because she legally owns my pet ferrets (we adopted them when I was a minor) Neither her nor my sister have the knowledge, ability, or time to care for the ferrets. She claims if I move out she will not let me take my ferrets with me which in time would end up with the ferrets having improper care and possible health problems along with developing depression, I would rather live here until she lets me leave than have the guilt of leaving my ferrets in an unreliable and unsafe environment.

EDIT 2: Thank you all for the responses, I have decided that a P.o. box would be the best option for my current situation. I will be looking into the process of getting one, thank you again.