I've been in the hospitality/service industry for 22+ years, and there's nothing more awkward than being bullied into doing something you know you're not supposed to do by a customer just because "so and so did it for me last time". There's no excuse for rudeness - ever - but saying no isn't necessarily being rude...it might be that person just trying to keep their job and being unwilling to break policy just because a co-worker has in the past.
The amount of money you've spent in a store should have ZERO effect on the general level of service provided to you or any of the other customers in the store at the same time as you, and frankly, walking into a store, any store, thinking that you've spent so much you should get special treatment is distasteful to me, at best.
I'm afraid that you've already given enough name and location info that your dear Manager Sara could be in danger of losing her job, if she has indeed been doing favors for you that she shouldn't be doing. We know reps from the brands read these forums, and we have a number of Coach employees here as members as well, probably many who read and don't post.
I think the bottom line for me is, if you want outlet pricing, go to an outlet. If you want to pay FP, go to a boutique. The two shouldn't be mixed and to think that the business model or management of the two types of stores is the same just because they all have the same brand name on their paychecks is naive. Do you think you should get the same level of service at a Fairfield Inn and at a JW Marriott Resort simply because all the employees receive their paychecks from Marriott? I think not.