Open circuit scuba has very few possible failure points and it it very easy to be critical of the woman and say she could have done A,B or C. There are a number of failures that could have caused an uncontrolled ascent or induced a panicked swim to the surface. A stuck inflator could be one or a lost weight belt or even just unusually rough water conditions or low visibility and a bit of wonky equipment. The relative volume change for the last ten feet of water could do it. There is very little to go on here and a lot of speculation may be about things that turn out to be unrelated to her death. For example, blood at the mouth may have from her getting bashed in the face while trying to get her back in the boat.
Until there are more specifics, this is a game of random speculation.