missing spot of hair

Hi, I am new to this. I have a cat named Priscilla who is over a year old. She takes baths with me all the time. Ever since she was a kitten, she has been getting in the shower with me. I went away for the weekend and when I got back I noticed a spot of fur missing near her shoulder blades. It appears to be a little irritated, but you can't really notice until you look really close. She has been scratching that area a lot lately. I took her in the shower with me last night and have been putting antibiotic ointment on it. Any suggestions??
p.s. I am also wondering what are all the symptoms of heats in a female cat and is there anything I can do to ease her symptoms? Thank you!!

Have you left her alone for the weekend before? Based on what you said, it sounds like it could be separation anxiety. Some cats get so anxious when their people leave that they will either scratch fur off, or pull it out as a nervous reaction. If it looks irritated, open, or infected, you may want to see your vet.

As far as a female going into heat, trust me you will know. She will yowl and carry on, probably be very affectionate, wiggle around on the ground, shove her rear end into anyone's face who is interested. You may also notice that her litterbox will smell stronger before and during heat.