one's selfishness could cause misfortune to another :)

and my guess is correct... it is pretty obvious the culprit was so cooperative

yup, if she had been patient and let the events flow as planned after her target was taken in for questioning, it would have been quite the pickle to pick the culprit out of the obvious pair of folks who hated that person.

she also made two other errors.

1 she was the one who had the power to pick and suggest listener submissions. therefore, she was obviously the one who had the power to 'slide that submission' into the show. if she had personally forged the submission, she could have given false contact information to a burner phone on it. when somebody called 'her' to confirm the listener submission, the part where her friend admitted the whole thing was fake wouldn't have happened. once her listener submission was confirmed she could have easily disassembled the burner phone, lit it on fire somewheres out of the way, then broken the SIM card into pieces and tossed it into the fire as well. with no connection to her the listener submission would have never led Conan to her.
...
2 she never should have personally asked the neighbors about the trash throwing lady's routines. she could have easily observed those routines without asking questions at the apartment complex. if she watched from a distance for a few weeks, she could have observed the barhopping. then with a few bills passed to a few bartenders with the quiet question, "I found a picture of that lady and my boyfriend on his phone. I think he's sleeping with her. Does she come here alot and maybe meet up with a guy? All I could tell from the picture was it was taken at a bar." one or more of the bartenders would have known the trash throwing lady goes drinking every Friday night.

Okay surprised that intro had a different narrator