My question involves landlord-tenant law in the State of: Illinois

I have a roommate that is refusing rent. Last (and first time) they paid was January. Their name is not on the lease nor did we sign anything. The electric bill is in their name. I have been asking for rent but keep getting refused it. The amount (250) of their part of the rent, half of electric , and half of water is what I asked for. We are at a 500 dollar electric bill (we fell behind for jan-feb and feb-marchs bill) which she claims to have paid (we still have electric on) so I told her that since my half of the rent is half of the electric I would pay for the entire bill of Feb's rent.

I did this because I don't want to hand my cash to this person in fear they don't pay the bill but I have offered several times to go and pay it with her. Problem now is March. It's almost going to be April and still no rent. What can I do? I fear this person will retaliate with my belongings since when she moved in I had everything in here. TV, Computer, Internet, Couches...etc. She brings questionable people in to the house and smokes weed even tho I have expressed my concern. She is only 18 (I'm over 25) and behaves like I owe her something. I need them out of the house or them paying rent....still considering giving a 30 day notice (after my past due rent is given).

Thanks.