The relationship between the two was going poorly, and they had in fact been living apart - a thousand miles apart - for five months before Lisa joined VWF in DC as supposedly "a last-ditch attempt to save the marriage." There was a pretty decent chance that each was seeing other people during that split up time. (That's merely some useful background.)
The life insurance policy paid off even in the event of "suicide" of the insured (quite unusual) but would certainly not have paid off if Lisa had participated in the murder plot. The fact is that there were powerful financial incentives for her to participate in the plot - and the cover-up of the murder as a "suicide." But these financial incentives would not be in place had she not seen to it that (1) the last insurance premium payment had been mailed and postmarked one day before the death and (2) the paperwork for the transfer of the oil leases from Vince's mother to Vince had been completed before the death. So the very fact that she told her husband to be sure to mail those two items from the WH on the day before the death was either (1) very good timing for Lisa by sheer coincidence or (2) sususpiciously suggestive that Lisa had foreknowledge of what was about to happen and was (affirmatively) preparing for it.
Lisa's actions on the day of the death and her avid participation in the cover-up are darn convincing of her involvement, to say nothing of the fact that she got lawyered up with a top notch Clintonista Washington criminal attorney immediately - despite the fact that she had only been in DC about a month.
I'm not saying she didn't participate in the cover up, but I just don't see any reason to assume she was complicit in the death itself.
My belief would be that she participated out of fear of the Clintons.
What I cannot understand about his family is why none of his children have sought greater knowledge about the death since they are already grown. Indeed, I suspect more fear.