Court fines and penalties?

Can my girlfriend go to prison for not paying her fine when her benifit was stopped for four month and she was getting no money, and she offered them what she could afford when she got her benifit reinstated. She has offered them money on the phone and via letter and they want it upfront all of it but she can only afford so much a month. Can she be put in prison because she couldent afford to pay it and because she had no money for four months