Hello Bill - I am sorry to read of the issues faced. The forum is used by HMLR to answer frequently asked Qs so you are posting with HMLR still involved in any reply.
The only B3 I am aware of would be a Land Charge but that's a means of protecting an interest created by a charge on unregistered land and that's not the case in your scenario it seems
The restrictions you are referring to are covered by our PG 24 -
Private trusts of land (PG24) - GOV.UK
And I would strongly recommend that you/she seeks legal advice to first establish what her legal position is, how her interest might be realised and if so how that might be protected on the land register
We can't advise you on the legal aspect but if PG 24 does not cover the registration guidance then needed our PG 19 may be of wider assistance -
Notices, restrictions and protection of third-party interests (PG19) - GOV.UK