No it is not legal unless the employee has committed an act of gross misconduct of such severity that such a summary dismissal is warranted. A disciplinary hearing and investigation, subject to the employee's right of appeal and representation is standard procedure.
The only reason why her manager did this is because he/she doesn't know the rules and/or they know they can get away with it.
They have been trying to get her to agree to change the terms and conditions of her employment by coercion, which is not only unethical but not lawful.
www.acas.gov.ukGive these guys a call and ask for advice. The more of you who are able to give statements the better. Make sure you note down times of meetings and who said what.
These guys are out to make a buck at the expense of the staff who's undertakings were transferred. Give them the kicking of their lives with my blessing.