Claire Gwendoline McMahon, 41, had always contested the case and was even charged with jumping bail during the court proceedings.
She was convicted that on September 14, 2016 she assaulted Celine Orthlieb in Devonshire Terrace.
McMahon originally entered a not guilty plea in March, last year and eventually came to trial in November.
She was already serving a sentence of fourteen weeks imprisonment and the three months was ordered to run concurrently to that so she will not be locked-up for extra time.
McMahon was also ordered to pay £400 compensation to the victim and a collection order was made.