Partially blind Yvonne Khan, of Walsall, set up stalls at locations including Mill Lane, Wolverhampton, and Dark Lane, Essington, but failed to pay proceeds to the charity.
She was found guilty of committing fraud against the charity between July 21, 2018, and August 16 last year and guilty of possession of articles in the use of fraud after a trial.
She denied all the charges against her.
The latter charge related to amendments to her supporter registration letter after it was emailed to her.
Chairman of the bench Mrs Michelle Wallis told Khan that her actions crossed the custody threshold.
Mrs Wallis said: "You have been found guilty of two charges, fraud and use of a letter.
"Myself and my bench colleagues have concerns about that offences of this nature have a detrimental effect impact on members of the public who make donations.
"And your actions may result in people reducing their support to charities and similar causes because they think money no longer reaches the people it should be helping."
"We are also concerned about the large scale operation you were running. You had five tables and a van. For those reasons we do feel these offences are of high culpability and of harm.
"However, we have taken into account that you have significant health concerns."
Khan, 62, of Clews Close, Caldmore, also ran stalls at sites on Studley and Stonleigh, in Warwickshire.
The court previously heard that her crimes came to light following concerns raised by another vendor over Khan’s “aggressive sales technique” and over the quality of the publicity signs used on her stand.
Camera footage of her in action was shown to the magistrates at the trial.
Mr Martin McNamara, mitigating for Khan, said: "She has found coming to court stressful. She accepts the findings and the court's decision. She is of low risk of re-offending and has limited means.
"She is remorseful and has accepted that she must be banned from car boot sales.
"She has donated to MacMillan Cancer Support in the past. She wishes to draw a line under it all."
Khan is now prohibited from car boot, jumble and table top sales for two years.
In addition she was sentenced to six months jail suspended for two years at Wolverhampton Magistrates' Court.
She must also attend 10 rehabilitation activity days with probation and was ordered to pay £1,615 costs within 28 days.
Giving evidence at the trial held month Khan said she suffered from dementia, epilepsy and is blind.
The case was brought by the charity as a private prosecution after Khan went to four car boot sales representing that she was selling items to raise money for MacMillan.