Felicia would basically be the MJ, and Morrigan the Black Cat between the two of them, I'd think. Felicia would probably be a lot more emotionally invested in both sides of Peter's life, whereas it'd primarily be Spider-Man that captures Morrigan's interest. The key difference between her and Black Cat however, isn't that she has no interest in the Peter Parker side of things, it's simply that she makes no distinction between the two. She'd be the exact sort of person who'd ask Peter why he can't just use his spider strength to do what he wants, and might not really understand why he might not want to. She doesn't know him beyond what she cares to know about him, so it's doubtful that she'd know about Uncle Ben unless Peter were to go out of his way to tell her, which I don't see happening unless there was more emotional investment on both sides.
Felicia? Oh, he'd definitely tell her, they'd have a good cry together, and she'd double down on supporting both Peter and Spidey in whatever ways she could. She might even consider assisting Spidey on one of his daily patrols, since she's more than capable of defending herself.>It's public knowledge that Pop Star Felicia is currently dating Daily Bugle Photographer Peter Parker>They're considered an odd couple, but nothing big is made of it>Eventually images of Felicia's outings with Spider-Man are leaked, and tabloids eat it the fuck up>Parker Luck strikes as Felicia's reputation tanks as a result; folks aren't buying that Spidey and Felicia are "just friends">Paparazzi are actively ruining both Peter and Felicia's lives>It takes a classic "Peter and someone else in the Spidey costume show up at the same time" maneuver to help clear the air and restore Felicia's reputation.