A scorned wife I do understand but Malini was outright ugly.
Mistress - A person having extramarital affair with a married man. leave aside validity of both marriages Imlie never ever gave anything reason to Malini to doubt that she is having a relationship with Aditya.
In fact she has mended their relationship way more than both of them together. The real reason for Malini's anger is Aditya but she is a coward who doesnt want to hear truth from him.
Her insecurity is with Aditya.. Imlie is not a reason for it.. Don's lash out on someone who is innocent in all that is happening. She was not being protective of Imlie.. She is just trying to break the weak link between Aditya and imlie. A 19 year old who has done nothing wrong (wearing sindoor not wearing it has to be a personal choice e.g Rekha)is being bullied by a 27-28 year old just because she thinks her husband is having an affection towards the girl.
Also about being maid.. a maid is being paid money... imlie is not.. so what Prakash described her to mithi works.. she is actually someone Aditya knows who is helping out in household stuff as T's are providing sheltor to her.
Use of big words need to done with a very logical explanation. A simple google search can be really helpful in this matter.