Go to the step family house at 9 pm and go upstaire, it should trigger the eventhow can i triger that mom visit step family house and have a argument mom and stepmom??
Edit : Oh wait I misread, I thought you were talking about neightbore mom, if it's mom, then you have to request that she have dinner with step family at 7pm, she will refuse at first, you need to wait some days before asking again, after the argument you will need to wait some days before asking again so both mom make peace at the step family dinner.