Get BT Support to speak to her when the problem is occurring. remember, you are paying for 24 hour support and there will always be someone there
Call them and get them to note there is an intermittent problem and when your homeworker has a spate of problem s she will call. They will call her back on a mobile number and the proceed to test the line in various ways including incoming calls with them running a remote acccess session to her PC.
If they find a copper pair fault they have a way to get it raised and resolved.
M H C
taurus excreta cerebrum vincit