Also for Chandra, i believe it been mentioned a few times that Chandra has always had feelings/a strong crush on MC since pre-story & current story. With current story MC can now accept any those feelings/desires for Chandra (besides being legal now) after many flirting and advances from her and i guess now MC not treating her as just "he's boss's kid daughter" he protected.
Example, when MC drove Abby home, they mentioned how Abby interfered with Chandra messing with a douchebag (to make MC jealous) during Chandra's sweet sixteen, so i don't think she went all the way sexually (not penetrative sex at least).
During the scene brunch meeting with Chandra giving MC some prime info, she gave off the impression that she's putting on a facade for MC at times and it shows that she isn't just a party girl and enjoys the finer things in life (brunch every weekend, etc.).
During that scene, I personally interpreted MC's "you were never innocent" line as that she always had a perverted mindset at a young age, combined with all the teasing and her rebelling against her mom Meredith. So, that probably was her first-time.
Well that's on thoughts on it