Looking at your profile, she's less than a month old? She SHOULD be attached to your breast and in your arms constantly. It's what newborns need... it helps milk supply and it's a protective instinct thing... she's been with you for 9 months straight, being separated is foreign.
As far as why she cries when she can hear/see you and doesn't when she can't. She doesn't have object permanence yet. She doesn't know that when you leave the room you still exist.... then you walk back in the room and she goes "oh yea, that lady... she'll take care of me, come hold me!"
Get a wrap or a sling and co-sleep. All us wacky babywearing, co-sleeping moms don't just do it because we're nuts... we were all once new moms with babies who wanted to do nothing but to nurse and be held. It will make your life 100x easier and save your sanity, I promise.
at 1:57 AM on Dec. 17, 2009