Read the article. Her mother was an artist and she did reproductions, especially Renoir.
Looks like she needed money and decided to chance it.
If she had needed money she sure didn’t get it by strealing the painting. Not sure mom even had the opportunity to paint reproduction and replace original with it. While the article states in 1957 she either graduated with her art degree or obtained her Masters Degree but it is not really clear which was accomplised in 1957 because of the poor manner that information was presented. So I doubt that she possessed the necessary skills to pull of a quality reproduction of Renoir. If, however, at whatever her age was in 1951, mom that is, possessed the talent to reproduce Renoir’s style then she could have supplied that to the actual art thief/thieves and stored the paining for them. But even that I see as doubtful. The article fails to really elaborate on her skills, but rather only insinuates the possibility since she apparently was know to have created reproductions.