Melissa's Wi-Fi is really slow of late. Leo says that everyone is experiencing bad Wi-Fi these days because we're doing more with it and dozens of devices are typically connected to it. Congestion is a serious problem. To eliminate her ISP as the problem, she should connect directly to her router and see how it performs. If it's just the same, then she'll know that the ISP needs to fix the problem. But if it improves, then it's her Wi-Fi network.
One way to solve it is through a Mesh router like the Eero, Ubiquity, and the Orbi. These are all good Mesh routers. They choose the best channel and frequency automatically. Plume is Leo's current favorite. They also have little plug in receivers that Melissa could put in every room to create little "pools" of 5 GHz Wi-Fi. It's expensive, but it works.
(Disclaimer: Eero is a sponsor)