Sometimes the humidifiers for the entire house don't do enough. Emily used to have lots of sinus congestion, etc. years ago and a room humidifier was suggested (we also have a whole house humidifier). We also purchased a monitor for the humidity level in her room (not expensive, just purchased it at the hardware store). And, we found that her room NEVER reached the level of humidity that was recommended - and this was with the humidifier in her room. I'm sorry, I can't remember what level of humidity was recommended but I'm sure it's on the packaging of the monitor...
Did she have the nosebleeds before starting LDN? I've never read of any connection but, if they started at the same time, maybe ask the question on the LDN subforum.