Do you cut back Lady Boothby at all? Not now is my advice! I'd wait until spring and see what you've got. If it's a hard winter the top growth may well not survive anyway. As it's pretty tough it would probably regrow from the roots in that case. Wait and see what happens.

P.S. If you need to trim a bit off to get past the old girl, just take off the minimum necessary for access.

i dont do anything to it until april, then i only remove the dead top growth.