Snooping Mother-In-Law Caught in the Act When She Triggers Hidden Glitter Bomb, Feigns Innocence, Plays Victim

When u/itsbettertobelucky realized that her mother-in-law was snooping she decided to catch her in the act. 

She went upstairs to see what her mother-in-law, who was supposed to just be using the bathroom, was up to and caught her well out of place. The mother-in-law just pretended that she had "gotten lost" upstairs on her way to the bathroom. As if.

When u/itsbettertobelucky approached her husband about it, he just brushed her off saying that she "Just get[s] annoyed at this because everything [the MIL] does drives [her] crazy." So u/itsbettertobelucky realized that she needed some hard evidence if her husband was going to believe her and deal with the issue with his mother.

They had the in-laws over for the holidays. u/itsbettertobelucky had previously attempted, at this point, to catch her mother-in-law in the act by putting glitter on door handles. That proved to not be effective enough. She needed harder evidence to undeniably catch her mother-in-law in the act. To achieve this she rigged an envelope, filled with glitter, over the door to the office. 

Lo and behold... The mother-in-law ends up covered in glitter for being where she's not supposed to. But now the husband and his family are taking the mother-in-law's side. 

u/itsbettertobelucky wants to know... Did she do the right thing? Who is the a**hole here?