Does My Sister Have To Show Up To Court?

Location: Illinois, USA.

My sister’s ex boyfriend filled out a notice of motion form for custody and left it in a family member’s mailbox at a home that my sister doesn’t even live at. It wasn’t properly served, mailed, handed to my sister or even notarized (notary section left completely blank). She also can’t find anything online about it. But she just found out the GAL (court ordered to represent her ex) will be attending the court hearing, but she hasn’t communicated anything about the court date with my sister at all.

We were assuming that my sister doesn’t have to show up to court (in this particular instance) but she doesn’t want her absence to make her look bad during this entire process and does not want to risk a default judgement against her (if even possible in this situation).

Additional context that might not all be relevant: My sister and her ex boyfriend are going through the child support/child custody process. Initially, he didn’t have any custody due to his his alcohol abuse but is now allowed to see her every other weekend. My sister also has a 2yr order of protection against him due to physical abuse (against her. Not my niece) and his threats to kill her.

He cannot contact my sister directly (because of the reasons stated above) So he messaged her through the parenting app saying that he would see her in court on the 6th. She was confused because they didn’t have anything scheduled for the 6th. She asked him what court was for and he didn’t respond.

Aside from everything above, he bought my 4yo niece a cell phone (my sister doesn’t agree and doesn’t think a 4yo needs a phone). He said it’s because he wanted to be able to contact his daughter anytime he wants.

My sister found out that he has a location app installed on that cell phone and it can only be disabled on his end. My sister is almost always with their daughter (unless she’s working) and on at least one occasion her ex has taken screenshots of their location and sent them to my sister inquiring about said location. Her ex now knows where her boyfriend lives and other locations my sister (and niece) have been to.

For this reason she turned the phone off and then her ex called the police “in a panic” to do a welfare check because he couldn’t get a hold of my niece on her cell phone. My sister doesn’t deny him calls or his agreed-upon visits, but his calls are supposed to be made through the parenting app.

Anyway - all this to ask if she needs to show up at this court hearing?