Validation on Possibly Fraudulent Account

I posted about this earlier but couldn't find it until today...

My deceased ex-girlfriend may have opened a couple of joint credit card accounts using my name as a co-signer. GEMoneyBank is now trying to collect from me. I vaguely remember signing something for her a couple of years ago, we split up, and about a year later she passed away.
I sent GEMB a letter asking for copies of the statements and the signed contract so I could tell if it was my responsibility. I received a packet of statements yesterday for ONE of the two accounts in question. The first statement they sent was dated six months after the "original purchase date", so I don't even know what was purchased! For a year and a half the statements were mailed to her address. I never saw them, was out of her life, plus she died about 6 months after the account was opened! To top it off my name is misspelled. Then they found me and started sending the bills to me, still misspelling my name. I have told them repeatedly that this is not my account, etc.
When they initially called me, about 6 months ago, they did not have any of my personal information (address, birth date, etc. - it was all hers) I have told them I don't think this is my problem. I have asked for a copy of the signed agreement - something with my signature on it but so far they haven't sent that. I have not paid anything and don't intend to, however it is growing and growing! Any suggestions?
Someone posted that if this is a fraudulent account that it is a matter for her estate. She definitely had NO estate. She left only bills! How do I get them to send me a copy of what they believe I signed so I can see if it even looks like my signature?