I released a walkthrough for Mom a couple of days ago here:
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For the redhead girlfriend: once you've heard the rumor from Nick, and you have > 80 influence with Emma, flirt with her during the evening. There's some RNG, but you should get the scene with the redhead about 20% of the time. Obviously there's no art for it, but there's a bit of a sex scene.
You can always flirt with Cassandra, just like the other girls: when you're at home (and Cassandra is out for the night), choose to text someone > text Cassandra > flirt with her.
Assuming the patch is enabled, the first time you flirt with her she calls you creepy, the second time she asks: "Did you text the wrong person? I'm your sister you weirdo," the third time she says: "Seriously [player]? Flirting with your sister?", and the fourth time she says "You keep sending me these flirtatious texts and I'm gonna start thinking you're serious." Once she's said that, you're on your way. You should have a scene with her the next evening when you are home.
As for Candace, if you are able to cast Corruption on her then you are on the path, just follow the walkthrough I posted above.