I've always theorized she pulled the gun out while taking pictures of him in the shower. Forced him to sit and shot him with her left hand. That would match the trajectory in my mind. I think the sound in the hard surfaced bathroom and shower would have been deafening, even with a little .25. I'm pretty sure the gun jammed so she had to run and grab a knife. I'm pretty sure she planned to shoot him and learned too late how ineffective her lack of skills, lack of caliber and lack of maintenance of the gun would be. Her grandfather stated the gun was really old and had belonged to his cousin but he came into possession of it when his cousin died. It had 7 rounds of jacket hollow points in it and he had no idea the make or serial number.
An old .25 would easily jam. In fact, it probably stovepiped, which means the casing from the first shell did not clear the ejection port fully and prevented more from firing. This most routinely happens when poor (or inexperienced) grip on the firearm allows it to recoil at such an angle that the port will not clear. Once she had finished stabbing him and washing him off in the shower, I think she collected the gun and cleared it, allowing the casing to fall where it landed (in that chaotic manner fully described elsewhere on WS) in a puddle of congealed blood.
But hey... just an idea....