Then how do you validate someone saying they haven't been sleeping good lately or that we should be out with friends. Those aren't feelings. And if the thing that I'm suppose to validate are the underlying feelings that she is having that leads to those statements then am I not assuming what her underlying feelings are?
You are right that you don't know what her feelings are unless she has affirmed that you 'got' them. However, a close educated guess done with an attitude of acceptance works wonders.
Why does someone have trouble sleeping? Usually it's because something is troubling to the point of not being able to shut off the thoughts. You might say, then "So this has been weighing heavily on you." Since you don't know the specifics yet, this will likely prompt more disclosure about what is bothering her.
To the "should be out with friends" you could respond: "So you miss socializing together."