3 month old baby and possible separation anxiety?

My daughter is 15 weeks old and has all of a sudden gotten in this--for lack of a better word--phase of screaming at the top of her lungs and crying huge fat alligator tears after I've left her (even for just a few minutes). She does this when I get home. Not when I leave or while I'm gone, but when I return and she sees me. It sounds like someone threw her down a flight of stairs, she's screaming so loud and crying so hard (its not a tantrum either, I know when she's throwing one of those lol). She's only done it to my in-laws. I leave her with them for 45 minutes to an hour tops just to run an errand or two. When we were visiting my family last month, she never did this to my parents even when I left her for a few hours. Could this be considered separation anxiety(even though she only does it when I come home)?...can a 3 month old infant even have separation anxiety? Her next doctor's appointment isn't til March 10th, and I fully intend on asking her about this, but in the mean time, does anyone know what it is and how I can prevent it?