As expected, she’s not only a female Hulk but also his cousin ala what Supergirl is to Superman. To put it simply, she got into an accident and Hulk kindly donated his blood to save her life. Somebody said that her popularity actually owes to the growth and acceptance of female bodybuilders, which could explain certain fanart (and sometimes official art) of her.
This makes sense given the timing of her publication. Unsurprisingly, some older readers remembered her as an awkward virago or a galoot as Mike Madrid called her. Perhaps amusingly her current series is a weird throwback to her initial presentation and description.