You are not obligated to use the agent. But, I wonder if there is a good reason you don't want to give her a chance. It sounds like she is trying very hard to start a positive relationship with you. You might want to consider at least meeting her to see if you think she will work that hard for you!
I hope this helps.
I would just say, that if you are interested in starting an active buying process and are thinking about using an agent, now would be a good time to look for one. Interview a few, ask your friends for referrals, chekc out Trulia profiles, etc - use several resources and go with someone who's professionalism you trust.
Every agent has access to MLS and can send you the updates on your property search. It would be beneficial to you if you run your searches through the agent whom you want to use, because once you see houses that you would like to look at, you can then click a couple of buttons and send a notification to your agent, who can then arrange showings to you. Communication will be easier. Many agents have "a search with a tweak" on their websites, there are providers who use same MLS info, but add extra features to the search, for example you can group your searches more easily, make notes, request showings etc.
Here's an example of what I use on my website:
Also, when you do choose another agent, please kindly let the other one know you want to be taken off her list. There usually is an unsubscribe button or link in the email, or you can just send a quick email. You don't have to go into details, something like "unsubscribe me please as I no longer need this service" should be enough.
Best of luck!
No, you have no obligation to her - as long as you didn't sign a contract stating she's representing you. If you do hire a different agent in the future, you might want to let her know you've hired someone and ask her to take you off her 'mailing list'.