Not complaining, just weirded out

Miss M, previously the worst sleeper in our ZIP code, has been essentially sleeping through the night.

Sometimes a snort or two (or a need to be flipped back to her tummy) at 3 or so, but really just going to sleep, after a nice long nurse, essentially BY HERSELF and then going and going and going until about 5. Then she wakes up crying, but stops as soon as she is cuddling with Ema, sometimes nurses, sometimes not. And then more sleeping until 7:30, 8, 8:30, or even (this happened yesterday!) until 9! We are clearly between teething episodes, but still...

I can't quite figure out what's going on. What happened to my child? Is this an alien changeling? Is there an 18 month growth spurt? Taxman says she is making up for all the sleep she missed in her first year and a half by being awake and screaming.

I promise I am not complaining. To tell the truth, I am kind of proud. We overcame all sorts of obnoxious advice and comments, including from medical professionals and relatives, about coddling her, nursing her at night, and generally responding to her versus letting her just cry and figure things out for herself. And now, after many months to the contrary, we are finally at peace at night. Well, everyone except for me. I'm still up, peeing and freaking out about the months to come.