It's occurred to her, in her current position, that it was probably not in her best interest to try that same window again.
The first time it would have worked. She'd studied the house enough that she recognized that the only way in (without having to work her way through several traps and devices) was the side window. She'd seen the Orc's going in and coming out through the same one every time there was movement to or fro. Her timing probably could have been better, but, how was she to know that a different group of explorers (thieves, adventurers, other Orcs?) would be kicking down the front door at the same time? Bad timing all around.
Of course, it's possible that she should have waited more than a few hours before trying that same route again. It's also possible that Ferro Sphene is not the most patient of her race.
At least she wasn't that poor Elven girl. The one bloody, bruised and violated shortly before death (and perhaps after death as well). Even the shadows Ferro decided to escape through were better than staying in that room full of stench.
And now, running. With her everything always seemed to end with turning in the opposite direction and running the hell away.