Baa is so evil

For 25 years she ruined Anupamaa's life & treated her like a slave. But now she has made Anupamaa her daughter.

IMO that is only because of selfish reasons. Now Anupamaa has grown a spine, so Baa has to be nice to make Anu agree to her wishes. She cannot order Anu around anymore. She has realised that only Anu can tolerate her torture & make her life comfortable. Her own son or his girlfriend will never happily let Baa treat them like slaves.

If Baa approved of Kavya has a daughter-in-law, she wouldn't have cared for Anupamaa at all.