Hello Debbie, please be assured this is perfectly normal behaviour for a new little one.
I am going through a similiar experience myself at the moment with my new hamster Cunning Ham. She came from a breeder so was very tame and used to being handled. She happpily let me play with her when I brought her home and all that night but the next day she developed a shy complex and is only now getting over it.
You have to respect their space when they first come to live with you and don't be worried if a night goes past when you don't even get the chance to touch them. The first week or so is a very important time in a new hamster's home. We must ensure we keep stress levels to a minimum, as they have delicate digestive systems.
If you are not feeding a hamster food with added pre-biotic (such as Harry Hamster) then can I suggest you obtain some and supplement her diet with it. Candace has really highlighted a major concern in new hamsters. Wet Tail is a dreadful condition and usually life-threatening. Her story is very sad and not totally uncommon. All of her lovely new furballs are fine though thank goodness. The source of the hamster and the conditions they were used to living in can have a major influence certainly.
Candace has given you some great advice. As she said give Molly a few nights to settle in offering treats etc. through the cage bars and open door if possible. Hold her ball up to her door if you can let Molly enter it this way. Sadly this is not possible certainly with cages that only open on the top.
Above all never open her house or poke your fingers in it. If she wants to hide then respect her wishes.
Talking to her you will soon find she starts to come out to see who and what you are. When she does gently touch her back only for a few days - don't be alarmed if she seems to flinch away from your touch at first, and run and hide in her house. When she doesn't immediately try and run into her house anymore it is time to try and hold her
Some people find it easier to then allow their hamster to enter an empty toilet roll tube and then let them walk out of this onto their hand. If you prefer just to pick her up be positive and use both hands - you may need to take the top off your cage to allow you to do this. Hesitating will make her nervous and may cause you to receive a nip. Try to hold her over the bed for the first few days as baby hamsters are notoriously like wet soap!
Only take her out for a few minutes and slowly build up the time over a week. You will find if you cup her in both hands and hold her near your heart it will help to soothe her. Talk throughout all handling episodes and always offer a scrummy treat when you return her to her cage.
Seriously you will soon have a little Molly coming to the door begging to come out whenever you call her name, like happily my furball is. A little patience really does pay off with these guys. Doing it this way they really seem to loose their nervousness a lot quicker than if we rush in and pick them up straight away against their will.
Hey it is hard to believe sometimes that I only got Cunning Ham on the 29th of March, she has come on so quickly. Having a hobby breeder hamster does help as her parents have great temperments certainly but this method has worked for me with rescues of all ages and the occassional petstore purchased hamster.