@Jerry Ellis I don't really understand why you nearly lost it, it sounds to me from what you have posted about this encounter that you did not have an agent, were looking for an agent, and she was offering her services. If she was not "your guy" then I don't see any obligation to actually let her know if you wanted to see anything additional, from the sound of it she didn't ask you to sign any sort of agency agreement.
The one important thing I want to note though in this situation, you were a customer to her and not a client. Her duty is to the seller if you are a customer and any information you give her on your own free will about your motivation or what kind of an offer you would be considering she has a duty to pass that information along to her seller. For example, if you told had perhaps told her you needed to move soon or that you were offering one amount in order to negotiate back to another.
I agree, you definitely need to vet an agent you are going to work with ahead of time to make sure you feel you can trust them, that you are their top priority, and that they will always look out for your best interest. There are a lot of agents out there who may not meet this criteria, either intentionally or unintentionally.
Something that agents will rarely tell you, your agency agreement is an employment contract with the brokerage, not that individual agent. If you are unsatisfied with your agent, you can contact the broker in charge to get a new agent or a lot of times they will allow termination of that contract.