I can only speak from using AT&T DSL,but I think you can only use one modem at a time with DSL. I think that it is more physics than policy,only one modem can operate at one time. Call Verizon & tell them the situation,maybe they could put a second line in to accomodate your wife. Personally,I have AT&T Fast DSL 6.0. I also have what was Charter Broadband,but is now Knology because Knology bought them out for our local service. I use AT&T for surfing the net,for Vonage VOIP,& for internet connection for my DIRECTV dvr receivers.AT&T has a very low fair use policy,so I have Knology for Roku,Sky Angel,etc.
Anyway,call Verizon,see if the price for an extra line would still be cheaper than keeping Comcast,& then go from there.