"Dear Mr. Lukeman, I've read three of your books and you've been an amazing inspiration. Thank you for all your work in adding to the writing community. I have a question - actually more of a worry. I was recently signed on by a new literary agent in a small agency. I was so excited to have landed an agent after a year of sending out over thirty queries that I signed the contract (after showing it to two lawyer friends who thought it was a standard contract). The agent is new, but she has over twenty years editorial experience in publishing and I know that she's in "acquire new clients" mode at the moment. But I've heard nothing from her since I signed the contract three weeks ago and she said she'd read my manuscript asap and help me polish it a bit more (minor changes) to get it ready for submissions. I sent her a friendly email ten days ago and no response. I know she's busy and I'm totally not the annoying type. I'm patient. But I'm also worried that I may have been hasty in signing a contract with someone who was abrupt on our phone chat (only gave me fifteen minutes) and didn't respond to my email. Should I be worried? Thanks so much. As always, your advice and guidance is greatly appreciated."
The first question is whether your agreement had an out clause--a termination clause that gives you the option to fire her. If it doesn't, then you have no choice, legally, but to stay with her. Practically, you could ask her to release you, but the choice is hers, and if she refuses, you owe her a commission, regardless of who sells it.
Whether she is competent or a good fit for you is a much harder question to answer. Just because she spoke to you for 15 minutes doesn't mean she's a bad agent; just because she hasn't responded to you in 3 weeks after promising edits doesn't mean she's bad either--reading and editing can take weeks, especially if it's long. It depends on the length of the manuscript. In general, it is always best to discuss timeframe upfront with an agent to get an idea of what to expect and avoid this situation. The fact that she hasn't answered an email in 10 days is more worrisome--but then again, she may have perceived herself as being pressured early on in the relationship. Hard to say. Email her again and see how quickly she answers, and what she has to say. I wouldn't necessarily worry now, but if she ignores you again, then there is cause for concern.
After a certain point you can turn the heat up and email and call. If she still doesn't answer, you may then want to fire her. But whether you can legally depends on your agreement.
In general, author/agent communication is always a tricky thing. It's always best to try to discuss these things openly upfront so that no one has any false expectations.