Since it sounds like she was up late, I wonder if she overslept that morning?
I'm thinking about a "helpful" neighbor. Notices Mollie trying to rush the dogs out to potty, maybe Mollie comments about running behind or oversleeping and not having a vehicle. Neighbor offers to take her to work and she accepts. She may have known the neighbor well enough to feel comfortable with riding with him or went against her better judgement so she wasn't late/later to work.
It would allow for the dogs to be taken out then put in the basement, no signs of a struggle, explain why her work shirt wasn't home. But because I haven't the foggiest idea about anything else, I don't know if it works with everything that's known. It does seem like someone in the neighborhood would have seen her taking the dogs out in the morning, but I suppose she might take them into the backyard or somewhere not so visible or no one noticed her because people are off in their own little worlds/suffering morning fog.