Is it normal for manager to not let me have a meal break at work?

I work 8-10 hours each day and when it comes time for my only break of the day which is 30 minutes long, I have to work.

What happens is I go in the breakroom, warm up my lunch/dinner meal and sit down and within 3 minutes, my manager comes in and tells me she was calling me over the loudspeaker. I've told her several times that this is when Patty schedules me for break but I had to stop because she never listens. So today, she marches in as usual and tells me I'm not allowed to ignore her calling me over the loud speaker and that I'm being unprofessional.

First I tell her, the speaker isn't in the breakroom so I don't always hear what's going on out there on the floor. She tells me I should always be listening even if it's low.

Then I ask her in a nice polite jokey way why I can't just eat my meal. She said, "oh don't play the victim with me, you're obviously allowed to eat your meal, you just have to be on call and listen"

So then I ask my usual question, "what was the page regarding?" and she said she needs me to help a customer out in my department for a few minutes.

This is when it gets even more annoying because I asked her "should I clock back in and then clock out when I get back so I can still get my 30?" Her response was, "No, just leave it be and when you get back, you can finish." So I said, "every time you tell me to go out there, you do realize I'm stuck out there for 20 minutes, right? That leaves me with less than 10 minutes break the entire day as I don't even get my 15 min breaks ever"

Then she says, "I don't care, I'm your manager and helping customers always comes before helping yourself. You're so selfish"

So I am finally pissed after this happening for several months straight and I said, "You actually have no right to take my only break away from me. You take over an hour break and you work the same hours as me. I see you in your office, everyone sees you. You order food, you sit there, you don't leave for sometimes 2 hours. Why are you allowed to take a 2 hour break and I'm not allowed any break?"

Then she says she thinks I'm self-centered and that I'm her employee, not the manager. She tells me managers have more rights than employees and that she only takes 30 minutes which is a lie as she even had her boyfriend in the office with her two days ago while she sat and chatted to him and ate sushi from 4pm to 6pm. She didn't even respond to pages.