If you are worried about whether she is actually in season or not, your Vet can do a test - some dogs have fluctuating hormones, which mean that they can start a season and then stop again, only to kick off again soon after. If you want to get her spayed, or find out if she is sexually mature, let your Vet check her hormones.
I didn't get Barley spayed, and I wish I had now - she has had several mammary cysts, and ultimately a complete strip down one side, but my Vet feels that her time is probably finite as they may have metastasised - earlier in her life, I just didn't want to put her through an Op if it wasn't necessary, and the other risks weren't fully taken on board then ....