My mother died last year, leaving money in her will. My sister is holding onto the money and is now claiming she will fight to keep it. Help?

Last December, my mother passed away due to cancer. Before she died, however, she took money out of her life insurance (ADB, since she was terminal) and put it in her will, which stated that my portion of the money gets automatically sent to my college and that the rest be given to me at 25. My stepfather was supposed to get his money about four months ago. However, my sister has time after time been difficult in giving us any sort of funds (Had to drop a college class because of not being able to buy textbooks, and also had to starve for a little bit. Almost late on lease payment, etc).
Now, my stepfather is planning on suing her. Apparently, he received an email from my sister's boyfriend stating that if we sued, they would also fight to keep the money. He talked to our old lawyer, and she apparently said we have a case. He also mentioned that the will left my mom's estate in his care, but my sister took a lot of mom's belongings with her. So he is planning to sue for theft as well.
Here's what I'm worried about. It seems to me that my sister will definitely fight in court to keep her money. I know I'm not giving out all the details, but is there a chance that she does win and end up keeping all the money? Is there anything we should research or look deeper into before making this decision?

EDIT: Bot told me to include location. I'm in North Carolina.