My peer recommender does not speak English as her first language. Will you judge my application based on her writing?

No. We'll evaluate your candidacy based on many factors, including what we learn from your references.

Choosing a peer who does not speak English as a first language or who may not be a highly accomplished writer won't reflect poorly on your candidacy. However, you do want to be sure that the person who writes your peer evaluation can write at a level that will allow her to clearly express the strengths and qualities that you have to share with others. If she can do that, then having her write the peer recommendation will be fine.