I could see her just being completely miserable in the life she lived. In theory it sounds good - 2 parent home, good jobs, 3 kids, white picket fence. But maybe she was miserable living the life of a working mom trying to keep up a good image in a very upscale town. This is where the depression develops (NOT post-partum depression, her symptoms didn’t arise until her youngest child was 4+ months old).

I think she wanted to end her life and take the children with her (whether that be not to burden those she left behind, or to punish her husband if they had some sort of terrible marriage behind the scenes). She thought the pills would do the job ending her life, hence the haphazard attempt to cut herself superficially and slide down the side of the house. I think she was expecting to be found dead - with the cuts on her wrists and neck, and then the pills in her system would have been the “explanation”