Hi there.

I have put off the main quest for around 80 hours. I got to Dragon Rising pretty early but never did it. If I were to complete this now, would Lydia be leveled at my level since she now spawned? Or is she set to a certain level when I first receive the quest?

I'm level 53 right now.

I think she is your level since she hasnt spawned yet.

She should be level 50, which is her maximum (like all housecarls).

If she's not at your level just use the Wabberjack on her. She'll turn into something, wabber again, and she should change back leveled up. That's what I used to do on my PS3 version.