I think several of the respondents to this thread have missed the point. She's talking about the OWNER of the store, NOT a salesperson. While 2 weeks may be appropriate in some places for service, it isn't in others. In both CT and AZ, my dealers tell me in advance how long a servicing of my machine will take. The OWNER is making a big mistake and alienating her customer by not responding in good faith to the phone calls.
I also agree that honey is better than vinegar in dealing with this woman, because you're going to have a long relationship with her if you keep your 'new' machine! Acknowledge that you know she's very busy, so you think you can find a buyer for your 'old' machine yourself.
I would be worried about future help with the 'new' machine, too. Did she provide a warranty that allows you to return it? Does she give free lessons? Most sewing machine dealers include them as part of the deal when you buy a machine. My dealers in BOTH AZ and CT do that with used as well as new machines. If she doesn't, you have a lot of learning on your own. I suggest that you ask sweetly if she will give you a few lessons, but do it in person, not by phone. If you have a warranty and can return the machine AND she won't give lessons, I'd be inclined to return the machine - unless you've figured out how to use it already by yourself!