Sharkey scored with a cross-court shot five minutes into the match, just as the royal visitor took his seat, dressed in a ParalympicsGB tracksuit.
And she scored the final two of GB’s three goals in as many minutes in the second half, following Jessica Luke’s successful shot along the right sideline.
Sharkey’s second came with a delivery down the middle that went over the top of the prone defender. An outstretched Danish foot was not enough to stop Sharkey’s next.
The only point at which GB were under pressure came at the end of the first half, when a penalty was given for a high ball, but the shot from Denmark went wide right.
Amy Ottaway, an 18 year old from Norwich, scored the fifth goal from a penalty shot in the final minute, having just taken the court as substitute for the first time in the tournament.
Ottaway, who admitted to being “a little bit in love with Prince Harry”, did not know the royal guest was in the arena.
“I found out afterwards and I screamed really loudly,” she said.
“It was my first court time. Jess had had two shots so she couldn’t take the penalty so I took it. It still hasn’t sunk in.
“We had already qualified for the quarter-finals but you want to go in with the most confidence you can have and to get such a comprehensive win definitely sets you up for the next round.”
Sharkey, from High Wycombe, was pleased to have royal patronage but happier that husband Frankie had managed to attend the game.
“Yes, it’s a privilege to have Prince Harry here but for anyone to come and watch us play is a great honour,” said the 24 year old.
“My husband hasn’t been able to make it to every match but he was here this morning so that was my best person in the crowd.”
The victory, following Sunday’s 3-1 win over Brazil, means Great Britain finish second in group C behind China, and will face the third-placed side in group D (decided by later matches on Tuesday) in the first knockout match.
“If you look at the other group, Japan are playing well; Sweden and the US are playing well,” said Sharkey.
“We’ve beaten Japan 3-0, beaten Sweden a couple of times this year. The USA are a powerful team but if we’re playing with our best defence we’ll give them the best game we can.
“It’s important for us not to feel dominated by the fact it’s a quarter-final. We need to just treat it like any other game.”
For more news and pictures from London 2012 go to the ParalympicsGB website: www.paralympics.org.uk/gb