renter who is not on the lease

OK. so here's the situation:
my boyfriend and i rented an apartment with the agreement that my friend wld pay for the rent with us (1/3 each). i assumed this person was responsible and BOY was i wrong! so she ended up taking my things and she and i got upset at each other, but we eventually worked things out. a few weeks later she sd that she was going to move in with her boyfriend. we had spoken about her staying to pay the lease many times before this because she mentioned that her boyfriend was leaving the state. anyway... she ended up leaving and sticking us with the rent and the bills. when she came back to get her stuff, we signed into an agreement stating that by 10/31/08 she wld pay the bills she neglected and the rest of her third of the lease (signed by me, my boyfriend, my mom, my mom's boyfriend, my "friend" and the guy that came with her). the date that she agreed to pay by was about 1 1/2 months away when it was initially signed to allow her ample time to get the money together. so now the money is due in a couple of weeks and she sends me an email stating that she wont be able to pay it. she said that her loan that she had planned to pay with had fallen through. she said her plans are to jus send me money when she can. what an irresponsible human being! i am SO angry and let down. i cant imagine that someone could do this to ANYONE! now i see why my mom always tells me to put EVERYTHING in writing NO MATTER WHAT! so....... will this document she and i signed legal obligate to pay this debt she owes me?? can i take her to court?? WHAT SHOULD I DO??? PLEASE HELP?~?~

File against your former roommate in small claims court for all money she owes you. At the hearing, show the signed agreement to the judge. You should receive a judgement for that amount. You can then garnish her wages, attach her bank accounts, or lien personal property to receive your money.

what is the cost for small claims court? obviously i need to money because i dont have much money. i dont know if i can afford to front the money.

It varies by state and even by city. Call the clerk of courts and ask.

thanks for your help!