16 year old notary letter for UK visit visa

I am applying for a visitor visa for my daughter to visit me in the UK, do I need a notary letter allowing her to travel unaccompanied as part of the application or will a personal letter suffice? I am getting conflicting advice. (I know I need a notarized letter to actually allow her to travel from her home country) Many thanks.
The UK visas web site gives a comprehensive list of the documents that are required. If it does not list a notarised letter (which I think unlikely) then no, it is not a requirement.

Presumably your daughter lives with her other parent, and so the letter giving permission for her to travel should come from that parent. Depending on the country this may not be necessary, and may not need to be notarised. I am fairly confident that it is not a UK requirement.