Fateh's mother is blinded not by Jasmine but by Fateh. she is like mera beta mere yeh, mera beta woh, mera beta is always rights types. So as long as fateh loves Jasmine, she will be love jasmine. if he loved a toenail, she would love the toenail.
Her behavior towards tejo reflects the stress her husband and machi are putting on her. I don't think she would care if Tejo disappeared as long as Fateh was OK.