Greep spent the next few hours cataloguing her bid for freedom, also using her phone to find a number for the church caretaker.
But the social media-savvy businesswoman's tweets soon caught the eye of local police, who managed to track down a warden with a spare key for the door.
Greep said: "I realised I was locked in so I started going through my phone book, thinking of all the people I could contact.
"I didn't want to bother anyone so I just started tweeting."
Greep said she tried to phone a few telephone numbers for church volunteers on the back of a leaflet within the building but couldn't get through.
She said: "I tried the doors but they were locked. I spotted some wine, too - I thought God probably wouldn't mind if I had some, if it really came to it, but in the end someone came and rescued me."
The businesswoman said she would have had to wait another four hours for the 6.30pm service had her tweets not been spotted by helpful locals.
She added: "I can't think of many better places to be stuck. It was so peaceful, I was all by myself, the sun was shining through the window - though I wouldn't have been quite so calm at night."
- PA