Hello, a client hired me for a project one week ago, however since I accepted the project (Few hours since she send me the offer) I have not heard back from her. I sent her a couple follow up messages simply to check for instructions as the project is hourly, but I don't have the required information from client's side to start working. So, since she has specified that the project will be for 40hrs / week, should I wait for her to respond back to me before applying for another project?
Clients are not obligated to respond to freelancers.
If you have already done the work that you can do on this project, and sent her a message requesting whatever further instructions you require, then you're done.
I don't even send the message twice. Once is enough.
The client may be busy. The client may be on a sailing trip across the Pacific Ocean.
As long as you're caught up with your work, don't worry about it.
If you have time, then yes, of course. Feel free to work on other projects for other clients.
re: "So, since she has specified that the project will be for 40hrs / week..."
I think there may be a misunderstanding on your part about this.
The setting you are seeing means that you can log a maximum of 40 hours per week.
This is the DEFAULT SETTING. The client did not specify this. She may not have even noticed this.
And even if she did intentionally leave that setting in place, it does not mean that you should work for 40 hours per week.
It means that is the maximum number of hours you can work. The client may only have ten minutes of work for you during any given week. Or 2 hours of work. Or zero hours. Clearly it is possible that you could work for another client, especially since it seems you currently are finished with all the work you can do for this one.