Depending on her age, activity level, types of activities engaged in, medical history, etc. this could mean anything.
For example, it is pretty common for older, bedridden people to come down with get a type of pneumonia - and this is just because they are bedridden and don't move around enough to clear the fluid from their lungs.
There is also a type of pneumonia that can occur a few weeks after a near-drowning, and this can occur at any age even in otehrwise healthy active children and young adults.
The possible lymph involvement could be part of the lung problem or could be something completely unrelated. It's very hard to guess - unfortunately this makes it very nerve-wracking for everyone.