She may be having a false pregnancy. If so, she will continue to have some vulva swelling and her breasts will enlarge. She may even produce milk. This can go on for weeks as her hormones will be out of whack. It can be very distressing for them as they will nest, go off their food, tummy may even enlarge, and lactate. She may start mothering or carrying around a favorite toy and become snappy or hostile, out of sorts. It's due to her hormones. Her vulva will decrease in size some, but it will never go back to pre-heat size. Her nipples may remain somewhat enlarged also. She's gone through puberty now and there's no turning back. I'd consult your vet and have her spayed as soon as you can. That will help her hormones go back to normal and you may stop the false pregnancy symptoms.
"Having heard all of this, you may choose to look the other way.....
but you can never say again that you did not know." William Wilberforce 1759-1833