boiler for 6 unit

am currently waiting for a heating contractor to see if the part is available. According to him it's an older boiler, bur a good boiler and they stopped making the parts, but he is trying to get it from an older catalog. Meanwhile, the tenant is driving me insane. In one of her rooms the radiators work. The rest of the house is warm though. Last night my maintenance man checked the temperature and it was 75 degrees. She is a section 8 tenant and likes it around 90 degrees. I'm afraid she will report me and I will get into trouble because the radiators are cold. In the meantime I've been looking into other alternatives for temparary heat. The building is older and the electrical isn't set up for space heaters (electric) they will pop the breaker. Any suggestions on how to handle this with the tenant?

Only 1 apartment out of 6 is having this problem because I believe her apartment is the furthest pipes from the boiler and it's not building enough pressure because the crack in the tube.