I'd say be vigilant for him asking for money to get out of his country and try to stop it. As a precaution, try to google him - his discord name or if he gave you his real name. If he is scammer (which is not unlikely) he's probably done this to others already. It is possible you find something on him specifically if he is a scammer (which sounds like he is). Try to find as much as possible. You can also try to use some of his messages to use in the google search if you can.

I was in a similar situation and I've found some messages the scammer sent which were identical to those received by my close one (they would use templates they sent out to multiple people). This was the only proof that managed to plant seeds of doubt and I then managed to make other cracks from there. Your mom sounds to be pretty deep so dig as deep as you possibly can for as much info you can is my personal advice.

Good news is there probably isn't any kid that plans to move to your room - bad news is there is risk of your mom losing her money and possibly get in debt as well. Sadly if this is true, your job is to prevent it. If you have other relatives you and she trust and will see this as an issue, ask them for help - since you already treated the scammer negatively in her eyes, she is less likely to trust you alone.

Good luck. It's not easy but can be done.