Ok, so for those who didn’t know, there were 2 original screenplays for the animated Beauty and the Beast. The first had Beauty’s wicked sisters. The second one condensed the sisters into one character: Aunt Marguerite. She moved into Belle’s mansion to look after the family after Belle’s mother died. Given that she was like a wicked stepmother and she was obsessed with getting wealth and power, is there any evidence to suggest she killed Belle’s mother?
The showreel for the Richard Purdum version of the script (produced for Disney's approval) strongly implies that Maurice's sister, the loathsome Marguerite, simply decided to come and freeload off of him.
There's no strong indication that she murdered his wife, not least because her death seems to have taken place some considerable time prior to Marguerite's arrival.