When first introduced in volume 2 she is a full face and rather condescending prudish woman who has a strong dislike of Katchoo which is probably because of her strong religious beliefs and the perceived effect she is having on Francine who was raised by her to think that Lesbianism was a sin. 
 
By the start of Volume 3 we see her as a much older woman in their flash forwards and while she maintains her dislike of Katchoo's influence she nevertheless puts her daughters happiness first and when Francine's marriage breaks down after 10 years she calls Katchoo to come and help.. implying she knows that their unrequited love is one thing that Fran needs to deal with to be happy. 
 
Much later in the series in one of its lighter moments it is revealed that Marie was a pin-up model in her youth. When she si tracked down and seemingly about to be exposed in a where-are-they-now type fashion she actually embraces the alter-ego of her modelling days and sets up a business of reproducing her own memorabilia for profit.