That's interesting! I had Lidia as a follower since the beginning and never dismissed her... this means that she is still lvl 1?
yeah pretty much.. though I'm not sure you can get Lydia to gain levels with anything else than the console 'disable' and then 'enable' commands...
You can check the followers health by opening console, clicking on the follower to select it, and then typing 'getav health' into the console. Health is pretty good measure on the lvl. My lydia is stuck at 140 or something, the housecarl I got from Riften is over 500... I was much higher lvl at the time.