How can I ask for a substantial raise?

I (27F) am coming up on a year at my job as an External Relations Manager at a nonprofit. My current salary is 70k. My colleague, with the same title and responsibilities, has a salary of 80k. The reason for this is that she had switched roles and ventured into the tech/marketing department but has since come back to the ERM position. Despite the switch back, she kept her 80k salary. My boss hired a new ERM and, while I don't know for certain, I think his salary is higher than mine. My boss also hired an executive assistant recently, and I'm positive her salary is very close to mine. The job posting had the salary range at 65k - 75k. I want my salary at 85k and I want to start making commission. Does anyone have experience in this? If so, what is the most respectful way to address all of this and ask for what I want?