Innocent people can lie for reasons unrelated to guilt in a crime. Wendi might have lied about certain details (and I believe she did) to avoid looking suspicious, to protect her family, or simply to mange the stress and pressure of testifying under immunity. Fear of being misunderstood, especially in a high-profile murder case where her brother was convicted and mother will soon be, could lead her to stretch / shade the truth or blatantly and consciously lie without being involved in the plot. Also, incase you forgot, per Jeff, Wendi is a pathological liar that lies all the time and for no particular reason – so factor that into the equation
Disclaimer – in the opinion I am expressing above, I am NOT saying I believe Wendi is innocent. I am simply disagreeing the with statement that innocent people have no need to lie which as I interpret it implies that because she lied she is guilty. I completely disagree with that type of ascertain and just want to be crystal clear it not a statement in support of her innocence.