I set the stage to third trimester (still no showing or moodlet). But she didn't start to show and she didn't get the pregnancy moodlet, but I also have the pregnancy mega mod, and the pregnancy scanner said she was pregnant (with triplets, so I changed that to just one baby). They tried for baby, she had a positive pregnancy test. I did a quick test (with some minor cheating) with a female teen and male young adult. If you download the woohoo part, there's Woohoo_AllowTeens which allows romantic interactions between adults and teens.
You have to adjust the settings to have it do what you want. It's a little odd to get used to how it works at first, I was confused until I realized 1 it works on EVERY computer (at least all that I've tried) and 2 it's easier to use the settings file (which only gets created AFTER you launch the game with the mod). I use MC command center from deaderpool (with the woohoo part he put on another site) in my game.