Every two days she comes to Rumah at 5pm, for the quest directive you need to talk to her then and there.
Something like 5 days after you got the impregnation animation you will get a notification to go talk to her, she might want to fuck first if she is picking herbs.
Two separate things you have to do to advance, they don't conflict with each other. If you got nothing else to do, just go to Rumah, skip to 4pm, skip another hour. If she doesn't show up, skip to 4pm, and then skip and hour. By the third time she will have shown up. She walks in through the main gate, then walks to just under where Tia stands when she stands next to her hut.