You can’t hire anyone new and the job you want is being performed by someone you know is retiring soon, but you can’t rush her into retirement, nor should you. So you need to bide your time. Learn from that person. Ask them if you can shadow them and have them mentor you. Learn what it is that got them the position in the first place. Accept that a promotion for you will have to wait. Get yourself ready to be that person when the time comes. There is something you can do now to prepare. Being resentful that the person isn’t retiring will only frustrate you more. Deal with what is true and become the natural choice for the job when the time comes.