Unfortunately, nobody here can tell you anything with any certainty about what the nodule is. However, you should know that 60% of solitary nodules are benign. It is possible the pneumonia gave her the nodule or it is from a prior infection, or some other disease which is not cancer.
I too had a nodule found in an xray last month when I went to the ER and was told I had pneumonia and oh yeah, we found this nodule. I too was scared and went nuts for 2 weeks. Now I have let it go and will just take it as it comes as best as I can.
You have every right to be scared. But try to keep it perspective for now until you know for sure. I wish you and your mom the best!