She doesn't seem unstable, she's twisting and turning herself into someone new with every wind, yet she seems believable in all of her personas. She can be what ever you want her to be, but she can't sustain it. Eventually she will revert back to the real Hillary. If she wins the nomination, she will be in competitive overdrive, and you will see her change the things that got her nominated, to what will get her elected.
Just a side note: If she says "at the end of the day" one more time, I'm going to throw something at my TV.