Drastic change in behaviour?

[LifeWithPets]

Hi everyone. This is a bit of a long story but I hope someone has time to help me out.

A few months ago, in mid January, my friends neighbour dumped her daughters hamsters on my friends door step. They are campbells by the looks of them.
The kid took the hamsters everywhere with her in her pockets. Took them outside to "play" with her friends and their hamsters. (As you could probably guess, this kid had multiple hams in the past but all of them died really young).
My friend kept them as long as she could but she couldnt handle it.
Morticia, now named Priscilla, was incredibly aggressive. She would lunge for your hand and wouldnt let go. Her sister, Wednesday, Is much better behaved. They were fighting so got split up. Morticia very rarely slept, she compulsively ran on her wheel. When she did sleep, it was only for an hour or so. Chloe addmitedly didnt feed them correctly (1/4 teaspoon of a crappy bird mix daily). Morticia would try her hardest to bite you if you went near her. Due to Chloe being unable to care for them efficiently, I told her I would take one and she would need to find a home for the other, as I unfortunately didn't have room for both. (If you are in Central Scotland and are able to take on Wednesday, please let me know!!)
Morticia, who we renamed Priscilla, came home with me yesterday.
She has been upgraded from a small pets at home cage to a medium sized bin (64l "very useful box" from B&Q) She could use her saucer correctly as it was too big (she is TINY!) so I gave her a smaller one. Now she can run on it properly.
Her diet was changed from what was described above to a mix of Harry Hamster and Burgess Supa Dwarf with a few Pets at Home nuggets, the amount is about 3 teaspoons.

After settling in, she let me stroke her, let me put my hand in the cage and even let me rearrange the cage while she was in it. She happily takes sunflower seeds from between my fingers (I'm too nervous to lay them out on my hand at the moment).
Except one wee nip to my boyfriends finger because he got too close, she hasnt bit the way she used to. She used to break the skin!
After using her wheel properly yesterday, she has finally slept for multiple hours! This morning she was only out for a minute or so while I refilled her bowl then went straight back to bed!
Can these slight changes improve her behaviour so much within 24 hours?

I am so sorry for how long this post is but I wanted to include all the details!