Most ADSL to VDSL conversions are built as
*'Self-installs' by the ISP's. This only requires us (Openreach) to perform the necessary work at the street cabinet (The green boxes you will sometimes see us working in, at the side of the road).
As regards the modem/router ......... again, most newer versions are both ADSL and VDSL compatible ?? Gone are the days of needing a separate VDSL modem. However, how the ISP can tell whether your friend is using a VDSL compatible router I'm guessing is by looking at the routers chipset ?? This bit is not my forte, so others may be able to help further.
* If your friend notices that her circuit deteriorates daily after the self-install has been performed, I would suggest she rings her ISP and raises a fault for an ELF (Early Life Failure). More often than not, it will be the internal wiring that causes the circuits speeds to be affected and is more noticeable on VDSL rather than an ADSL product.
Hope this helps.