She is (or they are: I suspect the latter) a highly problematic figure, because a lot of dates around her do not seem to fit - if she is one person who married her two husbands on Geni. There is very little evidence about her which can be taken as at all reliable. The supposition that her mother was an earlier and unrecorded wife of Boso solves some of the date issues (but only just, and at rather a stretch).
You can find some modern historians who accept that she was one person, and attribute rather sophisticated twentieth/twenty-first century motives to Hugh's marriage to her ("to extend his influence in Upper Burgundy, forsooth"). In my view this is highly anachronistic. Rulers then had to be pretty bloodthirsty to survive and prosper. If her son allowed her to marry the ruler of a contiguous "state", he faced a high likelihood of being dusted off his throne, and out of this world. I just can't conceive of it in the struggle for survival then (and against the extremely ambitious Hugh of Arles, to boot).
The only real reason for supposing her to be the same woman who married two people seems to me to be the inertia of historians following secondary rather than primary sources going back a thousand years or so; and that "Willa" or "Guilla" is not now a common name and she/they were in roughly the same area.
But nor is "Boso" a name you are likely to come across now. It was once a common first name. What seems to have doomed it to disappearance was that Abelard, in the early twelfth century, chose it as the name, in his dialogues intended to teach logic, of the idiot who always chooses the wrong thesis and always gets beaten in argument. A rather striking example of how intellect can affect fashion even in an age where literacy was relatively rare (although, of course, in southern France/Northern Italy, more common than in most places).
Mark