Howling:River pretending not to know Clara?

This is my first time posting one of these, so let's see if I can get my thoughts out right. Also, I have to say I'm a big River Song fan, so I might just be keeping my hopes up that she'll return!

Did anyone else find it strange that River Song seemed not to know Clara when they were introduced? This is the River who, having died, apparently knows all she'll ever know about the Doctor, but seems like she's never seen or heard of Clara. But after Clara is in the Doctor's time stream, she says "Spoilers", hinting that she knows who Clara is to the Doctor, and what's going to happen. She also seems to be familiar with the Doctor going to Trenzalore. I just feel like there's more going on here than meets the eye, especially since all of these characters have a propensity to lie.