A.S.
Most cats go into heat when they are about 4-8 months old. Usually around 6 months - so yes she is a perfect age to start going into heat. Usually heat lasts about 7-10 days. Unfortunately unless they become pregnant they can go into heat once a month. If you are financially unable to spay her I would look into low-cost spay and neuter clinics. As soon as she is out of heat get it done. Spaying does a myriad of beneficial things including elminating uterine cancer, lowering chance of mammary cancer, lowering unwanted behavior - like the howling. You can try some kitty pheromones in the house but those can get pricey too. Most people just put up with it. Good Luck and I hope you get some rest.