Sabriel doesn't have much of an opinion on Una, beyond respecting her as a potential student and an ally in the fight against Malicant.

Henry... Hmm. Sabriel definitely respects him as an older man of roughly the same social class as her, and she acknowledges that he has more life experience than her. But at the same time... He clearly has little to no experience with the supernatural or battle, and that, (Along with administering medical help to him two times) makes her feel a little protective of him, and it's possible that she might act in a slightly patronizing manner when it comes to magic/fighting if those topics come up in conversation with him.