Try transitioning her to a mattress/bed in your room. You can always start out with her (or daddy) and move into your own bed later. You can also keep her there for a bit after #2 arrives. If you co-sleep w/ number 2, then the waking shouldn't be as loud and probably won't wake your daughter.
You can move somewhat slowly for the transition, where you/hubby sleep with her on the floor mattress for a few weeks, then let her know you will be getting her to sleep and you will move into your own bed - right there - after she falls asleep. This worked pretty well for us, even after our son was born. I could put my son down and then get my older daughter down with cuddles, then move to my own bed. It worked very well and my son never woke his sister at night.
Oh, as for the window, you could put some bars on the outside (safe if there is a bed/dresser, etc. near the bed, too. The bars will also protect from child falling out window. When I lived alone and before an alarm system, I got a set of window locks that clamp down on the window track. This made me feel much safer and they held quite tight. It is a very inexpensive solution. Not all alarms will go off if a window is broken, only if the window is opened and the contact broken.
Good luck. I recommend the Nighttime Parenting book by Dr. Sears