> my mother-in-law just moved into a basement suite of a home that uses shaw for their services.
Shaw's official policy is that she requires her own account for her own suite -- she is not allowed to use any "WiFi" provided from "upstairs".
> is it possible to have a second phone modem in the same house so that she has her own phone number?
Yes, Shaw would want her to have her own Shaw Phone adapter. Shaw would run a coaxial-cable from the "demarcation-box" on the outside of the house, into the basement suite, and would connect their adapter to that newly-installed wall outlet. Probably, at no cost for "installation" to her -- Shaw considers it much better to add a monthly-paying customer by not charging for "installation" of the new coaxial cabling.
You might want to investigate a VOIP ("Voice Over Internet Protocol") device. It will give her own telephone-number. But, there are "setup" issues, before the VOIP device can "receive" telephone calls -- need to configuration "port-forwarding" on the Shaw router that is "upstairs", so that the incoming traffic is not "blocked" by the router's "firewall" rules.
