We don't know this. Perhaps she became uncooperative ater police suggested to her Sherin is no longer alive? We have no idea how much she helped before this or what she is doing now.
As of right now, we do not know what Mom has been doing. She's innocent as far as we can be concerned... currently.
I was going off of what the Richardson public information officer, SGT Perlich, had said two or three nights ago while being interviewed. I am in no way accusing the mother of being guilty of anything. I was just saying she stopped cooperating after the first day.
BANFIELD: And I guess between your comments, I`m going to read between the lines. You gave me a fact pattern that did not include that mysterious road trip, which is extremely curious in this fact pattern. What about his wife, Sini, Sini Matthews? And I don`t know if I`m pronouncing it right.
It could be Sini Matthews. You`ve interviewed her, as well. What`s your read on the wife, what she knows, what she has said and whether she knows anything at all about this?
PERLICH: Obviously, we`ve done extensive interviews with her, as well. We`d like to do some additional interviews with her. Unfortunately, the attorney that she has does not wish to do that at this particular time. Our understanding is, from what we`re being told, was that she was asleep during the time that he took the child outside.
[20:10:04]BANFIELD: You were being told that by Wesley Matthews or by Sini herself that she was asleep?
PERLICH: By the two of them.
BANFIELD: And did you feel that the way that was reported to you was believable?
PERLICH: Well, that`s what we have to work off of and that`s what we`re trying to either prove or disprove. And that`s where we`re at with this particular investigation.
BANFIELD: Let me ask you this. Polygraph -- did either of them agree to, were they asked to take a poly?
PERLICH: By the time we got to the point where we would offer a polygraph, they were no longer cooperating with us.
BANFIELD: So neither one of them is cooperating now. They both lawyered up with separate lawyers, and that`s it for police interviews with these two, who apparently have a missing child somewhere out there, correct?
PERLICH: That is correct. And so we`re having to work off of the information we were able to gain from them on the initial day that she was reported missing.
http://www.cnn.com/TRANSCRIPTS/1710/16/ptab.01.html
The entire interview is linked.