Not proud that I drink but not ashamed either

I drink, obviously. I don’t drink a lot and I’d like to think I drink responsibly. I’m not ashamed of my drinking and I don’t regret that I started to. Today when I was trying to take my bottle of rum to the kitchen, my roommate stopped me. Told me she’ll get me my glasses to our room. This happened last week too. I live with 4 other people. I couldn’t figure out why she wouldn’t let me out of the room, I wasn’t even drunk yet. So when I asked her why, she told me she didn’t want to think right then. That’s when realisation hit me. She was ashamed that her roommate drinks. I still don’t get why she is ashamed when I, myself am not. What do you guys think!?