I've had a look at the original and was surprised to find that the transcription is correct! This means that the original was probably a phonetic rendering of Chew Magna, Somerset - as suggested by several other people.
I can imagine a person with a broad Somerset accent saying their birth place to a Welsh speaking ennumerator ...... BUT... I've also looked for the family on other censuses and she does seem to have a problem over her birthplace.
In 1891 it is given as just Gloster.
When did she marry Nathan LOVELL?
I haven't found the family in 1871
Were Robert & Edwin her sons?
You mentioned her maiden name was SCAMP and a Sarah SCAMP of the right age living in the parish of St Philip & Jacob Bristol in 1841.
From the baptisms in Bristol available on CD from the Bristol & Avon FHS
www.bafhs.org.uk Sarah Jane SCAMP d/o Peter & Mary Ann SCAMP was christened at St Augustine's Church, Bristol - 6th July 1834.
Best wishes
Pat