Mavis initially joined the Kabin in 1973 after spending two years at the Mark Brittain Warehouse as a clerk. Following a temporary move with her parents to Grange-over-Sands, she was re-hired at the Kabin and balanced her work there with nursing her bed-ridden auntie Edie Platt. Mavis finally escaped her overbearing relative in 1977 when she moved into The Kabin flat, where she led a quiet life with her pet budgie Harriet.
Mavis was to remain at the Kabin for over two decades, chiefly thanks to her strong friendship with the newsagent's manageress Rita Littlewood. Confident and glamorous, Rita took the shy spinster under her wing and a bond was formed. The 24 years they worked behind the counter together weren't without their lows; a born fusspot, Mavis often tested Rita's patience with her indecisiveness while Rita frequently took Mavis's loyalty for granted. Mavis longed to break out of her shell and in 1997 she retired to Cartmel to run a bed and breakfast.
There were few men in Mavis's life, and those who did show an interest, namely Jerry Booth, Derek Wilton and Victor Pendlebury, were just as dithering as Mavis and romance struggled to blossom. After a ten-year on/off relationship, Mavis and Derek were finally married in 1988, their second wedding day after a disastrous 1984 date in which neither the bride nor bridegroom had showed up at the church. Two years later, the Wiltons became the first owners of 4 Coronation Street, where the pompous couple regularly fell victim to the practical jokes of neighbour Des Barnes.
Mavis's move to Carmel came six months after Derek's sudden death from a heart attack. Finding it difficult to remain in Coronation Street without him, Mavis left Weatherfield for Cartmel where she remains to this day.
In 1983, her life changed, when not one, but two, men wanted to marry her. She wanted both of them, but had to choose between Victor Pendlebury or Derek Wilton. In the end she choose Derek, but jilted him at the altar as she wasn't convinced of the strength of her feelings for him. Her guilt at having done this turned to indignation when she learned that Derek had jilted her too, as he felt the same.
However, Mavis finally decided Derek was the man for her. When Mavis finally said "I do" to him in November 1988, she meant it. Her marriage to Derek was an unusual one - the other residents of Coronation Street looked upon them as something of a joke, but neither cared as they had each other. They would spend evenings reading aloud to each other from the newspapers and discussing the events of the day.
Their happiness was cut short in April 1997, when Derek died suddenly. Mavis was quick to hit out at his funeral at the people who had considered them a joke, saying that they had loved each other and that was all that mattered.
Mavis surprised Rita when she suggested that they should go into business together. They discussed the possibility of running a guest house in Cartmel, a town in the Lake District. Rita went along with this for a while, but both realised it was a bad idea - as Rita said "We'd end up throttling each other before t'week were out." Mavis went ahead with the idea, bought the guest house, and Mavis and Rita had an emotional farewell, ending a partnership of twenty-five years.
- In her early one-off appearances from 1971 to 1972, the character was credited as "Miss Riley".
- Thelma Barlow had quit the role of Mavis in 1997 after playing the character for twenty-five years. However, it was originally believed that she had quit the role due to the axing of her colleague Peter Baldwin, who played Mavis's husband Derek Wilton, who was axed by producer Brian Park. Despite this popular belief, Thelma confirmed on the programme This Morning in 2010 that she had quit the role before Mr Park came to the decision of axing Derek.
- Rita Sullivan visited Mavis in 1998 and 1999 at her home in Cartmel, and they holidayed on a cruise together in 2002. Emily Bishop stayed with Mavis in July 2004. In 2012 Rita attempted to visit Mavis, but was pulled over for speeding by a colleague of Kirsty Soames who was trying to get Tina McIntyre into trouble. Rita took a weekday break in February 2015, to visit Mavis who had recently lost nine pounds from a diet. In September 2017, Rita told Gemma that she wished she invested more in her relationship with Mavis since she left Weatherfield as they currently only exchanged birthday and Christmas cards.
First and last lines
"Excuse me." (First line, to Ena Sharples)
"I hope you will be too." (Final line, in response to Rita Sullivan's wish that she'll be happy in her new life)