all three of my children had and my smallest now has chronic nasal congestion, food allergies/environmental allergies and asthma. my youngest is two months old and his is worse than the other two. we are also having chronic ear/sinus infections with him, soon to see ENT because in just two months he's had three infections. anyways, this could be related to reflux. reflux can be a result of many things including an intolerance to formula, overfeeding or simply just a weak sphinctor muscle that will get stronger with age. reflux then can cause pain/crying fits, choking, and congestion. you can try to switch formulas and add a reflux med to minimize the acid production, though it won't fix it completely. although possible it is unlikely that she is having allergic reactions to the environment. the way our allergist explained it is that it takes about two years of exposure to environmental allergens for the body to react and build enough IgE to cause a reaction. although in rare cases it can happen. i would probably assume the formula and reflux are working hand in hand in causing the congestion. but only an allergy test can determine if the cats are the culprit or not. in the mean time, elevation, nasal drops, a cool mist humidifier all might help but that's as good as it gets. good luck. sorry for the pain your little grand daughter is going through.