This is an emergency. You will need to get her into an ER tonight. It sounds like she has a urinary tract obstruction and that can be very serious and deadly if not treated promptly. This is usually caused by a stone in a young cat like yours. Your vet can relieve the distended bladder and see if there is a stone in the bladder with either an xray or ultrasound. This usually requires surgery to cure the problem.
Let me know if you have more questions.
If you try and feel where her bladder is and see if that is painful to her on the lower belly - if you feel an orange shaped mass or larger, most likely this is obstruction. In this case, there is nothing you can do. Your vet will have to relieve the pressure with either a needle and syringe or catheter.
You might make it until morning if she isn't distended with her bladder. If you are SURE there is NO urine coming out and she is drinking, then she is obstructed.
Sometimes they have a urinary tract infection and have increased urgency and frequency but get some urine out, a small amount usually.