Thank you for your question. In a baby this young I would recommend seeking a consultation so that the practitioner can examine the baby and ascertain where the specific problem lies. In the interim I would recommend continuing with the saline drops but I would consider adding some Tea Tree oil to her humidifier. A method I prefer especially for kids is to simply use a bowl of hot water with a couple of drops of the oil in it. Hold the child over the rising steam with a towel over their heads. This is more direct and more faster than a room humidifier.
The first supplement/medicine I would recommend would be a good broad spectrum probiotic. This often proves to be enough of an immune stimulus to assist the baby to overcome the infection she is current;y dealing with. Any probiotic from the fridge section of your health shop will suffice - empty the capsule into her first bottle of the day for at least a month.
If she develops a fever that refuses to come down despite lukewarm washing and paracetamol syrup, or if she stops feeding or seems less conscious I would strongly recommend taking her through to your paediatrician, GP pr emergency room for a consult immediately.
Many thanks and warm regards