Hi and welcome!
When you let her out, I hope you are out also. Sadly, underground fencing is very dangerous… call the closest 10 shelters to find how many dogs they pick up with collars. They get excited, run through it, then can't come back. Also, while it might normally keep your dog in, it won't keep others OUT. But with supervision, they are GREAT so that they get freedom but you are there if a problem arises.