Well in theory (eg i haven't tested this yet), you could friendzone everyone to get the +1 love point triggered by "admitted that he had a girlfriend before but broke up with all of them". So you can pass the Judgement (insert dredd meme), then ask everyone (exceptions for palla, lexi or audrey, and ?Bree?) for a second chance. Recollar if necessary to update the status
Reading the wiki for Emma, quest "Girlfriend situation":
If a girl has any of these statuses she will count as a girlfriend: girlfriend, fiance, mistress, pet, sex slave.
If you catch Cassidy into a trap, she becomes your pet, that's her actual status. She doesn't have a friendzone option as far as I can see in the game (22.1 version).
We only need 1 lovepoint and NOT having Emma suspicious of cheating her in order to get her. I have no idea how she becomes suspicious - if anyone knows how that happens and how to avoid it, please share the info.
What I did (Emma wiki events):
"Handjob scene (5th date)" - "We're all out of Benji episodes. What now?"
"Cinema date" - "I like the this" -> 1 love point
"Eavesdrop on Emma and Bree" -> I have no idea if I got the point, Bree was in the home harem, wasn't collared, had sex with Bree, Emma and Bree both had 50 lesbian points. Emma didn't comment Bree being in the harem during the dialogue.
"Girlfriend situation" - total fail, no point
"The Judgment" - ok, "I think I'm falling for you", Emma doesn't leave
There's no need to be obsessed with "Girlfriend situation" event so much to get Emma. Rather, would be best to wait and avoid home hareming Bree until you pass the "Eavesdrop on Emma and Bree" event. Just to be sure.
Frankly, the devs shouldn't regard pet and sex slave status as a girlfriend.