I gave calcium, warm bathes, heating pad under Rubbermaid with damp towel and lid as vet prescribed. No luck. I think this is her first egg. How long can she walk around with it? she seems exhausted
Welcome to BYC.
The vent contracting is normal. They do this pretty much all the time.
Sometimes it will take a while for the first egg to come, so leave her in the coop/run with the rest of the flock and see if she will lay her egg.
Stress can make it more difficult, so if you still have her separated, place her in a quiet calm area with food and water and see if she will lay her egg. Hold off on the vent checks for a little while and let her relax.
If you can, put a little ky jelly or coconut oil no more than an inch (1") inside the vent to help lubricate. Make sure she is drinking plenty of water, you can also give her extra calcium by crushing a Tums and feeding it to her.
It sounds like she is stressed which will make it harder to expel. Hopefully she will calm a bit and get it out.