First off, that stretching hamster picture is absolutely priceless. I could think of so many captions to go with it.
And to answer your question, it sounds to me like she's a happy girl
My Wibbles would make a similar noise all the time. Especially when I would give him sunflower seeds. I think a soft chattering sound is fine, but if it is loud and sounds like hissing or popping, it probably means back off. With Wibbles, I figured out how to make the sound with my lips (sort of like a really soft kiss), and when I did it, he would chatter with me
On the other end of the spectrum, my Jasper used to make this ridiculous noise frequently. It sounded like he was saying "PEW!" I wondered if he was sick, or scared, or unhappy, when I first heard it. Then I heard him do it when I gave him one of those sweet treat blocks, and again when he took a sand bath, and I realized his ridiculously loud PEW sound meant he was happy. It was quite cute, though not at 4 am.