We would not feel a need to describe her by using a noun that represents her role towards him. She is just a stewardess who happens to be looking after him.The woman is looking after Nicky. If she isn't Nicky's carer what is she?
She might say:I don't think she could say: 'That is your stewardess.'
This was one of the stewardesses on the flight. She took care of me.How would Nicky describe the function of the person who looked after him on the plane?
Nicky's mom would tell him "This lady will take care of you. You listen to her and obey her. If you have a problem, she will help you".What the stewardess does is called "watching him" or "looking after him" or "minding him".
In the UK, carers are people who provides care for someone (though they may also have an emotional attachment), e.g. Young carers are children under 18 with caring responsibilities. A parent carer is someone over 18 who provides care to a disabled child ..."Carer" means someone who "cares" (feels emotions), not someone who "cares for" a child..