Personally I hardly believe she HAS any amnesia at all. If you consider what transpired in episode 2 and at the end of episode 1 you just might get what I mean.
Also, the pacing of first episode was perfect, you probably didn't notice the several things that happened there and what was also shown in the episode 2.
The fact that Yuuko is in reality quite an ominous existence.
Hint one: I'll skip a few things in episode 1 but at the end of if ep 1 you can evidently see Yuuko on the roof with a big ass angry shadow.
Hint two: actually quite a lot of them, Yuuko is being shown in a lulzy way in her ominous state, but when he stands in front of the mirror you can see the evil Yuuko there, her ominous self is visible throught the episode actually several times. And the rumors start somewhere, Yuuko is the cause of all of them.
Inb4, i did not read the source material (yet) but i wonder how correct I am.
First episode was very informative, second just explained how it all started there.
Having amnesia is one thing, but knowing how cell phones work without asking about it means she doesn't really have amnesia. She probably didn't care about it till then. I'm sure she doesn't know WHO locked her in that room though and that is what she will try to uncover.