If the bank tells you the check is not good to cash, call your neighbor and ask her for the cash. If she refuses, you will have to deposit that check into your account to have proof the check is bad. The check will be presented to her bank twice (this happens automatically) and if her bank refuses it twice, you will get the check back marked "ins or insufficient or account closed" or whatever reason the bank is refusing payment. Only then will you have proof. That also means that your bank is going to charge you a "returned deposited item fee" each time the check is returned.
You could give the,check to the local police and they might pay her a visit or you can go to your district attorney. Usually, for such a small amount, you will be advised to take the case through small claims court.
If these are remedies you don't want to pursue, you could just chalk it up to "living and learning" and be thankful it was only a couple hundred dollars.
I'm hoping you get the money tomorrow. You are not a doormat for trying to help your neighbor. You have a kind heart.