As a target shooter here in the US, I actually own a variant of the the Browning High Power, aka P-35 or GP-35. I don't shoot it often, but I took it out of my safe yesterday, checked to make sure it was empty, and examined it. For safety reasons, I would never point it at myself, period.
I did ascertain that I could grip the pistol awkwardly, and pull the trigger with my thumb. In my opinion, it is an unnatural way to pull the trigger, but it's possible to shoot it that way. As far as recoil goes, while the weight of the pistol absorbs some of the recoil, I personally wouldn't call it soft, but it has less recoil than some other pistols. Recoil is perceived differently by different people. Although there are variants with aluminum frames, most GP-35s are all steeI, and weigh more than most modern pistols with polymer frames. The weight of all metal pistols does make recoil softer.
I think that the weight of the pistol might cause her shooting hand to come to rest on her chest instead of the side of her body. It's a heavy pistol, and would probably force her hand and arm down on her chest if there was no conscious movement from her arm to prevent it. Recoil in this pistol wouldn't cause the pistol to fly out of her hand or off the bed. Still, there's nothing to disprove that someone didn't place the pistol in her hand, or even force her to pull the trigger.
As to whether this was murder or suicide, I still lean towards murder. There are too many odd anomalies to call this a suicide.