Update:
One of the biggest concerns when doing this was being able to sponsor the transfer of visa for her one employee to her new business entity, that has now been approved by immigration.
So she has now split her partnership (not formal legal partnership, but contractual arrangement) and used her sole-pro entity to re-employee the one staff she has.
The sol pro was not the main trading entity for her business (the vast majority of the modest revenue went through the partnership business that employed her 1 staff) and thus the sole pro, whilst 4 yrs old, had a very very small trading footprint - doesn't even have a business bank account.
So great that we've been able to get immigration to play ball. (I spent a lot of time carefully building the case to present to them).