Yeah, I wouldn’t file a complaint for this. Professors are often busy and difficult to reach over the summer, especially if they have to travel for research. It’s very common for assistant professors at top programs to travel a lot - they have to become internationally known in order to get the letters of support they need for tenure.
Are you sure that she rejected your proposal because of the topic or was there something else about the proposal that made her reject it? It does sound like you may have picked an advisor whose interests are not your interests, which generally is not a good idea.
Either way, it will take far less of your time for you to just find another advisor who can allow you to work on the project you want.