It sounds like the OP's daughter is intending to use the landlord's broadband via the WiFi in the landlord's house. As others have suggested, it is highly likely that the signal will not be strong enough to go through two sets of external walls.
A good signal meter app will confirm this.
InSSIDer (for Windows and Mac) is invaluable in this respect. Shows all visible WiFi networks and their signal strength in real-time, so you can walk around and see where the strong/weak spots are.
While I doubt the landlord would be happy to have his/her telephone master socket or WiFi router moved, running an external-grade Ethernet cable between the two properties would be an ideal solution.
Connect one end of said cable to the landlord's router and at the other end attach a WiFi access point (not a router!). Both properties then have independent high-quality WiFi on one broadband connection. Problem solved.
As much as I dislike them for the RF noise they throw out, power-line networking might also be an option - but probably not cheaper than the Ethernet cable and definitely less reliable.