Cats come can come in heat quite frequently, especially in the warmer months!!
Mine came in heat frequently like your cat is doing. And it was so annoying!! The meowing and the spraying was too much to handle. So as soon as they came out of heat, which wouldn't last long, I immediately took them to get them spayed!! Cats are horrible when they are in heat!! So now all 3 of mine are spayed and have been for awhile and I no longer have to put up with the meowing and spraying and them sticking their butt up in the air all the time!!
Good luck with your cat, try to get her spayed as soon as you can!!