That's fair. Was hoping you might have a clever way to flag them as they were acquired and unhide them on a master list.
2 tips, just in case...
Open up the Skills and hover over each skill. It shows you the list of that Skill/Topic's 'sub topics'. It's helpful to be aware of those. For example, Competitive is a sub-topic of Aggression, therefore it gives Aggression xp.
The girls (and Dad)
tend to talk about things that they're Interested in.
If you're looking for a tag to train 1 girl with, check the character sheets of the other girls to see who might want to talk about that topic because they're already interested in it.
No matter what can I get Gina to "Inviting" waited a few days like someone in the thread mentioned previously. Does her lust need to be leveled to a certain point for it to show up?
Adding Interests doesn't have any requirements beyond getting them to 100% in the 2 relevant skills.
Just a matter of finding the 'Thumbs up' icon to encourage.
For 1 or 2 of Gina's ATs you need to see her at the Bar for that.
Is Gina the only one with an open door at night?
Yes.
And you can sleep in her bed with her.