I've heard all sorts of unconfirmed claims with regards to the gunshot wound, including that it was a shot to the heart which either deflected or traveled around due to the angle of the shot entering her body and affected the stomach as well. I've never seen any confirmation that she was shot directly in the stomach.
If it was in fact a shot to the stomach, I don't think that would discount either murder or suicide. There are still vital organs in that area. And, if it was a murderer, I can see him taking whatever shot he could get based on the fact that she would likely be trying to fight back or trying to curl into a ball out of fear.
For the sake of argument -- and even though I am leaning towards suicide -- let's say the killer opens the trunk and aims the gun at Rita. She grabs the gun and the first shot goes off, missing her completely. The second shot hits the chest, stomach or whatever. It may not be ideal placement, but at that point, 2 gunshots have gone off and the police are on the phone. Gunshots will attract attention in the area, and the police are already on the way. So, at that point, toss the gun in the trunk, slam it shut and take off. No time to waste putting more bullets in her to insure a fatality. Odds are she will die before the police get there anyways, which she did. Or, if it's a stranger, she probably won't be able to give a good description because, allegedly, she didn't get a good look since he bashed her over the head and she spent the whole day in the trunk, until he opened it after dark and shot her. Even if she survived, I don't think there'd be a great chance that she could ID him.
Of course, while the first shot could have come from a struggle with an assailant and a misfired bullet, I think it could also come from someone staging a suicide. It would make sense that if you want to appear to have been murdered, that 2 bullets found in the trunk would make most people think it was a murder instead. Most people who commit suicide only take one shot. Two bullets fired would muddy the waters. So it's possible that she purposely fired the gun at something else before shooting herself. Or maybe she was nervous and shaky hands made her shot off the mark. For the second shot, she could have then placed the gun directly against her chest to assure the second bullet would find its mark.
ETA: Keep in mind, too, that this could have been a staged kidnapping and that suicide was never meant to be carried out. If you were looking to start up a go fund me account to raise money for financial troubles, a dream wedding, etc., a case where a woman was abducted and shot but saved by the police could most certainly generate a lot of donations for her recovery. She may have never intended to actually kill herself, but wound herself enough for donations to start pouring in. Unfortunately in this day and age, plenty of people have run scams to collect donations, up to and including things like faking cancer. So it's possible that if she did shoot herself she believed the wound to be of a non-fatal variety and that the police would show up in time to save her.
