Private investigator stalking me (crazy motherinlaw)?

ok... so about a month ago my husbands mother decided to hire a private investigator to follow me around while my husbands in jail (for stupid speeding tickets causing a revoked license) because supposedly, me having to get up every morning and go to work (around people heaven forbid) as a receptionist at a clinic and then driving home only to go to sleep and do it all over again the next day is "BEING A WHOS CHEATING" Anyways, this woman is a psychopath obviously I dont need to go in to details about that because thats obvious enough from my first run on sentence. So because of her stupidity, she decided to use her last few unemployment checks to hire a private investigator to follow me around. This investigator sent my husband a package in jail full of BULLSHIT. They got all my phone records and circled numbers that call my phone that I dont even answered for and says there people Im cheating with when the numbers are friggin solicitors!! I dont understand how this is legal!!!! My question is, how far can an investigator go to try to 'prove" you guilty of something? Also, my husband contacted me and told me she sent him stuff from my facebook too!!! I dont know if he's lieing or what because he wont go into details but I checked to see every IP address from computers going on my facebook and there is, in fact, a whole bunch from IP addresses that arnt mine!! I've changed my pword a bunch of times but I dont know how this investigator is doing this!! Can FaceBook give the investigator permission to do this?!?! Is any of this even legal!!! I get TONS of stuff through emails for my bank account, is she gunna give his mother my bank account info next. I'm so confused I dont know what to do. If anyone, knows please help me.