If she is self employed she is legally not an employee.
I would say she would fall under Article 5(3)
(3) Any duty imposed by articles 8 to 22 or by regulations made under article 24 on the responsible person in respect of premises shall also be imposed on every person, other than the responsible person referred to in paragraphs (1) and (2), who has, to any extent, control of those premises so far as the requirements relate to matters within his control.
She is not an employer in the workplace so she is not an RP, so article 22 does not apply.
The responsibility to ensure she is adequately trained is her responsibility.
The responsibility to ensure she is adequately trained to be on that particular premises still rests with the RP (two doctors). This is clear within article 20
(2) The responsible person must ensure that any person working in his undertaking who is not his employee is provided with appropriate instructions and comprehensible and relevant information regarding any risks to that person.
Let’s be clear. It is NOT their duty to train her. It is to ensure she is trained, and that she receives site specific information and procedures.