Ishwari is attempting suicide not becoz her son has fallen in love...
But becoz, she is angry on herself for not being happy for his son and for not being a good mother... She is unhappy about herself, she thinks she failed to be a good mother... in this desperation she is forced to take this drastic step. This step is not deliberate. She is not doing this to separate Dev n Sona... Ishwari is not an evil woman. She is not a psycho. She is just desperate.
She will surely repent and come to her senses when she will calm down in the hospital. But in the meanwhile everyone will misunderstand this and think that she is not happy about Dev getting married. RR may blow this issue out of proportion... So Dev-Sona separation...
This is just my POV...