Your friend will need to verify that the shell has adequate space first, that expanding the liner will actually provide more room once it is back in the shell.Wider, especially to make room for the big toe
"My friend" had pressure at the 10 o'clock area on the right big toe and 2 o'clock on the left. Shells seemed to have space in those areas -- the front of the liner tapered more than the shell. Bootfitter removed stitching on the front of the liner, made vertical slits in the liner material so it could expand where needed. I put the liner on and weighted it so the foot would extend the liner as much as it needed. While weighted, bootfitter duct taped the end of the liner to hold the cut fabric in place (and cover the gaps in the fabric).
I was told that if I need additional room at, say, the 9 o'clock area, I can just replicate what he did.