Sounds like good advice, as someone else said she must collect all paperwork of the business account/books as evidence. Plus she needs a copy of her employment contract/tenancy agreement if she has one. Also evidence in the form of letters (bank statements, electric bills, council tax etc...) that she has been resident there for last two years. Also bank statements proving that he has been paying her wages for that time too. Obviously passports/personal documents etc... just in case.
She needs to see a solicitor (housing) asap as he is breaking landlord/tenant rights. You can get free advice appointments from some solicitors.
If he wishes to evict her he must give notice in writing or obtain a court order, info here and www.direct.gov.uk/en/HomeAndCommunity/Privaterenting/Problemsanddisputes/DG_189241 here.
If she doesn't have a written tenancy agreement, she is still a tenant:
If the property is in England or Wales, then it is clear that she is a tenant. The landlord will therefore have to give her an eviction notice, under section 21 of the Housing Act 1988. He can then apply for possession, once the notice period has passed.
This is because: if she is present with the landlord's permission, she is not a squatter. She is a lawful occupier, and thus is either a licencee or a tenant.
If the occupier has exclusive possession of the premises, then a tenancy arises, not a licence. With a landlord who was not living there originally, it will be difficult for him to show that she (or the tenants collectively, if more than one) does not have exclusive possession of the property, since the tenant clearly can't be sharing possession with the landlord.
A tenancy is valid even if it is agreed verbally. As rent is due under the agreement, so the landlord says, then it is a valid tenancy. If there are rent arrears, that is common enough - it does not prevent there being a tenancy.
A shorthold tenancy is valid if created verbally. It will be a periodic tenancy (i.e. no initial fixed term). The period will be a month, if the agreement was for rent to be payable monthly.
A verbal tenancy can't be ended under section 8 of the 1988 Act, so the existence of rent arrears is not a ground for possession either. To obtain possession the landlord would have to give a section 21 notice.
If she has done what he has said she has (his reason for the eviction, which of course she hasn't) then why hasn't he called the Police? The court will ask this question too if he tries to use as an excuse.