She was estranged from both of her daughters at different points and states in (http://www.ohshutuprose.com/2017/08/the-accurate-conception.html) one episode (https://goldengirlsfashion.com/2018/03/24/artificial-insemination-and-old-lace/) that she screamed for the governess whenever Rebecca would cry as a baby. In other episodes, it’s made clear that she wasn’t comfortable with children/babies and wasn’t very maternal.

Blanche also alludes to the fact that she was an absent mother. She rather for Rebecca to not have the baby in the Miami hospital because she cares more about how a doctor might perceive her for having a baby via artificial insemination. And she rather give up (http://www.ohshutuprose.com/2015/09/bringing-up-baby.html) one of her kids to Dorothy so she can have a Mercedes (https://goldengirls.fandom.com/wiki/Bringing_Up_Baby).

Yes Blanche was definitely the worst mother. Sophia though may take that honor especially in the later seasons when she was just mean and cruel to Dorothy for laughs.

Yes, Blanche was the worst and I would have written it that she and Janet never reconciled.