I feel like, in the scenario you provided, it may not be necessary to update the charge nurse and request her assessment in the way you depicted. If you need a second set of eyes, or if the patient is declining to the point of a possible rapid or upgrade, then by all means, ask away! But as you learn to trust your own assessment skills more, you'll find that you don't always need a second nurse's opinion. Like others said, the charge nurse should be updated on major stuff, but you will learn which things can be done safely on your own. Still, never let a person's attitude discourage you if it is in the best interest of your patient.
I am three years in, and I still have to ask questions of my charge nurse. The best feeling has been when she asked ME for an opinion.
You will get there! In the meantime, pay the attitude no mind. Check in with other coworkers too, as you can often find mentors outside of management and leadership roles. And, for my part, I think I little light self-deprecation always helps: "Oh my God, Megan, if I haven't already annoyed the hell out of you today, get ready for this!" Insert sigh, smile, and patient care concern here.
You could always ask her, too. At a point when neither of you is busy, ask for pointers on using her as a resource and what she thinks you may be able to be more independent with. If it's something you aren't comfortable with yet, at least you'll have an open dialogue about your concerns, and she'll know that you are actually doing your job to the best of your ability and are willing to learn from her.