LAWS OF UTANG

good day!i hope you can help me with my problem.i borrowed P20,000.00 from my siister's friend.She lend me the said amount but I have to pay a 20% interest monthly & when I failed to do so I should add up a 200pesos daily penalty.It was last January that I borrowed the money, she let me sign with a paper under a certain microfinance that I was a co-borrower for a certain person I dont even know.I did because I badly needed the money, I already paid P22,000.00 but she still demands fro P32,000.00 since the said money was returned 6mos after. I only ask her to lower the interest since I was recently had an operation & cant afford to pay her that huge amount.She said she would file a case against me in the brgy, but I dont see the brgy as a proper venue because they only humiliate the person & really I dont find any proper settlement except for people will atlk about you afterwards.Is there any way that I have the right not to attend the invitation & can I file against the said person since she harrasses me a lot.I hope you could help me.Many thanks.GBU