I have a sister that I believe has suffered some sort of mental health snap. Is there a department there than can help with mental health

Yes there is

Yes. There is a 24 hour emergency room with a psyhiciatrist on call at all times.

If she is having a crisis that can end on her hurting herself or others call 911 so she can be taken and directed to the help she needs but if she is only withdrawn, depressed and she is willing to go with you to the stroger ER and you tell the doctor that she need help with her depression and he will giver her madication and a referral to see a psychiatrist