IMO
I think "helping HB with problems about breast feeding" was the story she gave HB in order to get HB to meet with her at the car and here is why I believe that.
Linking the interview with TM below and at 4:15 in that interview is where Tim talks about what MF told him.
We have seen in other cases where there are bits of truth the guilty person will give people and I think we got a little truth about the story she told HB to lure her out to the car that day.
She claimed to TM that her last conversation with HB was around 8:30 am that morning where there was talk about problems breast feeding.
I am betting MF told HB that she had a solution for whatever breast feeding problem was brought up OR maybe it was simply MF telling her she had given birth to her fake baby and wanted HB to come see it.
When TM was talking to her about the last time she spoke with HB I think a little truth slipped out on what the actual discussion was about that lured HB down to the car. Since MF told TM that the discussion was about breast feeding I have to wonder if that was the ruse she used to get HB down to the car to meet with her.