When the App is working it will give a reasonably good measure of the wifi strength. If its saying its good but user experience says differently - then there may be something else going on.
How is she connecting on wifi - that is - what device(s) are experiencing the issues? Have you tested and run speed tests on a laptop/computer in her room?
What Hub model is it and what package are you on?
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John
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I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired, 1 WiFi, 1 on PA) Hub5 in modem mode with Apple Airport Extreme Router +2 Airport Express's. On 250Mbps, Talk Anytime Phone, x2 Mobile SIM only iPhones.