Morgan is very unobvious with that mechanic.
She has a hidden (well, now visible in the latest patreon version) "masculinity meter" that gets increased or reduced based on responses that you give her in chat actions (Like "Yeah, you were terrified" would give -1, whereas you were never scared will give +1). Chat actions happen when you call her or buy her a drink. I don't remember exactly, but I think she has 4 thresholds - 80 (camo pants / jacket, 60 - jacked / jeans, 40 - sweater / jeans, 20 - sweater skirt), her hairstyle also changes, as well as responses she gives to talk actions (travels, tv, people, etc)
The trick is that as long as she is above 50 points, all lines that reduce her "masculinity" reduce her love points by 1. (and vice versa). So just go to bar dates, buy her a drink, say the "feminizing line", compliment her, or otherwise negate -1 lp, rinse and repeat.
As of now, her lp can never go above 100 (50% love bar) because the event that is supposed to advance her does not exist, so you can't get her pregnant without cheating.