I can see nothing in your post that points to a problem with BT's service. However I can see a clear suggestion that malware is behind the problem.
Get your friend to download and install the free version of Malwarebytes Anti-Malware:
https://www.malwarebytes.org/free/
(She should take care to ensure that she deselects the pre-selected option to install a free trial of the paid-for 'PRO' version).
She should then run a (so-called) 'quick scan'. (I've written 'so-called' because it usually takes over half an hour to run!).
When it ends she should click on the button to view the results.
She should then ensure that there's a tick placed alongside everything in the list and then click on the button to remove all the entries.