How can my aunt claim maintenance from her ex husband

Sir/mam my aunt got divorced 15years back till date she is taken care by her father. She was given property worth 1.2cr as gift deed. She gets a rent of 10k on it. So my question is what is the monthly maintenance or permanent alimony she can get from his ex husband. By the way they have 2 children, both are graduates and are doing jobs. My aunt's husband is working in bank and gets nearly 15-16 lacs per annum. He remarried and have 2 children of 10 years and 8 years old.