v0.9 stable:
i've removed that happiness indicator. it just confused everyone.
basically, happier you can get her, longer she will stream. but after 10 days it will get more and more likely she goes on a break.
as for happiness, each npc spawns with a factor thats multiplied to the base pay and thats their "self-worth". greedy characters want more, whores wants less, others vary.
same calculations are used for camgirls, she has a number in her head she wants to get. if she doesnt get it, she's unhappy.
it's up to you to provide with good enough service so she can get what she wants. marketing, net quality, policies, ...
thats pretty much it.
now some traits (blue balls, top performer, idol, ...) contribute to how much money they make. so you can lower their cut and they'll still be happy.