Hi BlueSwim - I did some looking at the 2014 Intel STS rule guide.
It looks like you need someone to complete the Project Recommendation form:
Project Recommendation: completed online by the person closest to the student’s research. The head of a lab should only complete this if he or she worked with the student closely.
If you are not working with a mentor, is there another teacher that you can talk with, bring up to speed about your project, and ask to complete the paperwork? That person may not necessarily have to be working directly on the project. Maybe you should talk with a school administrator, explain the situation and your desire to apply to Intel STS and other advanced competitions, and see if they can help you procure the help of a teacher? (You also have to have an "Educator Recommendation and a High School Report completed by a school official.) You could explain to a teacher what you had been working on with the previous mentor, etc., and in your paperwork, you could explain the history. Is it possible that you could talk with the previous mentor, explaining that you understand that she is unable to continue actively mentoring you but seeing if she could help complete the form since she is most aware of the project you are doing?
Trying to find a replacement mentor to help you further your research is, of course, a good thing as you continue to prepare for and work toward these advanced competitions. But you may want to tackle the two problems separately!
Here is the url for the 2014 rules PDF: http://www.societyforscience.org/document.doc?id=403
Let us know how it goes! And good luck with your continued research.