I can't say Angela Thompson was the worst mom. But she was pretty negligent and emotionally distant. She definitely never wanted kids. Though she did take some amount of care for the ones she had. 

She favored Sybil more because Sybil was much better at math, physics and astronomy than Danae. Which wasn't really fair to Danae. Danae was plenty smart, but she wasn't a prodigy in math and physics like Sybil. Also given more time and support, Danae could've excelled at all three. But Angela wasn't too interested in taking her time on this.

Needless to say, Danae and Sybil still have a lot to talk about. Even if Danae hasn't figured out how to say it yet.