Piotrowska was behind the till of the shop in London Road, when a male pulled out a gun from his bag, pointed it at her and said "open the till, love."
Portsmouth News has reported that instead of giving him the cash, the 29-year-old mum-of-one pushed him away and tried to get out of the shop.
Piotrowska said: “I could not believe it when he pulled out the gun. I said "What? I'm not opening my till. If you want money go to work.
“I grabbed the mobile phone and tried to dial 999. He tried to get into the till but I pulled out the key, pushed him into the shelves and walked quickly to the door, but he grabbed my arm and we got into a struggle and I kicked him.
“There was no way I was going to give him my money. We work so hard here I wasn't just about to give it away. My instinct wasn't to be scared, it was to protect my business.”
The man fled empty-handed and police were at the scene within minutes of the incident, which occurred at midday on Saturday.
Along with her partner Nigel Russell, Monika reopened the shop just an hour later and it was business as usual. The shop has only been open since October but the couple say an attempted armed robbery isn't enough to scare them off.
Mr Russell, 38, said: 'The police couldn't believe it when I told them what happened. They said "For God's sake give them the money if it happens again. The police have been amazing.'
Lee Knight, 27, of Stamshaw, Portsmouth has been charged with attempted robbery, possession of a firearm and possession of a bladed article. He will appear before Portsmouth Magistrates' Court today.
Police are still appealing for witnesses.