If it turns out that BB had not yet left for the airport as it's looking now, and even if somehow the story continues to be that she didn't know Maleah had been "brought back" by DV, his not bothering to wait until her departure means he did not have any concern about her discovering his efforts to be alone with Maleah in the apartment. Which obviously speaks to her complicity, probably over a long period of time.
What if the "fight" QX talked about before her trip was not about explicit phone photos at all, but about Maleah? This is pure speculation:
* BB is home on Tuesday morning getting ready for her trip. DV leaves with the kids to do the daycare drop-off.
* He returns at 7:54 and Maleah is with him. BB is genuinely not pleased about this, so they fight. Maybe she tells DV to take Maleah to daycare. He knows she won't do anything, so he either lies and says he will, or he just refuses.
* BB believes her trip is still more important than her child's safety, so instead of delaying or canceling her trip, she hopes for the best and leaves for the airport.
Honestly, her intentions could absolutely be way more horrible than this, too. I think this might be the best possible scenario in terms of how BB truly cared for Maleah.