Maybe the friend is jealous of the mom's life. For example, if the mom has a happy family or a successful career, the friend might feel envious and try to gain some advantage over her through blackmail.
Another motive could be revenge. Maybe he has some grudge against the son and he thinks blackmailing the mom is a way to get back at him. He figures it will cause chaos in the family and make the son unhappy.
That's a really disturbing situation. However, this kind of blackmail is completely unethical. In a normal family and social environment, such things should not be allowed to happen. If such a situation occurred, the mom should seek help immediately, like contacting the police or getting support from other family members.
Well, perhaps the mom's friend found out something she did in the past, something that could damage her reputation. So during summer break, when they have more time together, the friend decides to blackmail her. It might be related to an affair or a financial misstep that the mom made long ago. And the mom is now in a difficult situation, not knowing how to deal with this blackmail without causing more trouble for herself.
Well, it could be that the son's friend has some sort of secret about the mom that he's using to blackmail her. Maybe she made a mistake in the past that she doesn't want her son or others to know about.
Well, here's a story. A mom has a teenage son who gets into trouble with some bad kids. These kids find out that the mom once had a minor traffic violation she never reported properly. They try to blackmail her by saying they'll tell the police about it if she doesn't pay them. The mom, being smart, contacts the local community center for help. They work with her to talk to the kids' parents and resolve the situation without giving in to the blackmail.
There could be various scenarios. Maybe the son's friend found out some embarrassing or compromising secret about the mom. For example, he might have seen her doing something she didn't want others to know. He then used this information to blackmail her, perhaps asking for money or some special favors in return. This would put the mom in a very difficult and stressful situation as she has to deal with this threat while also trying to protect her family's reputation.
One way could be for the mom to confront the son's friend directly and tell him that she won't be blackmailed. She could threaten to go to the authorities if he doesn't stop.