Have SS visit her and then lock her up afterwards based on these threats.
The Secret Service probably didn’t take the threats John Wilkes Booth was making seriously, either. Since it’s a known fact that some actors think they are so much smarter and important than anybody else they should have a Veto over the life of the POTUS if he doesn’t agree with them. Lock her and any other celebrity making threats up until he’s out of office and then put a tracking device on them and monitor their locations for as long as they live. That ought to shut them up!