Re: Is it okay....
I'd have to fully understand the set up before I were to say for sure. But, as long as she can hear the baby, the garage door is close and the temp is safe, I'd be fine with it. I have done this many times with my kids. We have an attached garage. Now, our vehicle is too big to park in there so I can't do this. In the past, I've left the car windows open and the door from the garage to the house open and left the baby sleeping in the car. I wouldn't if it was too hot or if the garage door to the outside was open or if I could not easily hear the child.
I really don't see the difference in this and leaving your child in a room upstairs as long as you can hear them and they are safe (with temp and closed garage).
Heather SAHM to 6 who are 7 and under, including 2 sets of twins and our last little miracle, a surviving identical twin, born Oct 2012!