You can read about bona vacantia here.
http://www.bonavacantia.gov.uk/output/companie s.aspx
The last paragraph is significant because it indicates that the Crown usually declines to take over 'onerous assets' - and quotes the private road situation as an example.
I suspect your friend is going to need paid-for legal advice, because it may not be in her best interests to have the asset (the land on which the road sits) transferred to her. You also mention that 3 other properties are impacted.
She is going to have to look at the wording of the easement (private right of way) that she has to access across this land, and any restriction (obligation to the freeholder - the company that the Crown is in the process of dissolving) to pay for maintenance of it.
What won't happen (IMO) is that the Crown offers to transfer the road to part of the public road network - and the road becomes adopted - which means maintained at public expense by the local authority.
The Crown can't take her legal right of access away - and no-one else is likely to want to buy the land.
What is the nature of the link between the private road and the company in liquidation? - is it a property developer, or the business premises of a bust company that just happens to be at the top of the road?