How does my mother evict her adult grandchild and the grandchild’s boyfriend. My mother is afraid to confront them.

Are the grandchild and boyfriend tenants who are paying rent, or is your mother allowing them to stay out of the goodness of her heart so that they are guests?

If they are just guests, they don't have any rights to speak of. If you mother is afraid to ask them to move out, or if she asks and they refuse, she *could* go to the police and essentially file a trespassing complaint against them. This has *tremendous* implications for future family relations so it's something that should not be done lightly, but that is the process--guests have to leave when you ask them to, if they don't, you can go to the police.

If they are tenants--so they've been paying rent (or paying some other cost, such as contributing to the food budget or utilities or taxes in a consistent way that could be considered rent)--then the question is, is there a lease or not? If there's a lease, what does it say--what is the term? You mother could ask them to leave when the  term is up, and if they don't then instead of the "trespass" scenario, she would go through the process for  eviction, which will mean filing the proper legal action (probably with the help of a housing attorney specializing in representing landlords vs. tenants).

If there's no lease but the grandchild and boyfriend pay rent, then the term is taken to be month to month, and your mother can ask them to move out at the end of the month. If they don't, it's the eviction process.

Note again that things could get ugly; if your mother is physically afraid (and not merely afraid of confrontations) you may need to get a protective order, or at least informally speak with your police to appraise them of the situation and ask their advice, in advance.