that really depends on the type of hamster. The gestation period for a syrian hamster (also known as a teddy bear hamster or a Golden hamster) is 16- 18 days. For a dwarf hamster it is slightly longer, 18-21 days.
You have to see how long it is over the gestation period. If it is really over the gestation period, your hamster may not even be pregnant at all. There are cases of false pregnancy where the hamster is not pregnant just showing the signs of pregnancy or it could have reabsorbed all the pups.
Don't put your GP and hamster together period! Even if you had Your hamster longer its irrelevant they still fight ! Plz DO NOT them together for there sake!! The GP will probably kill the Hamster !! trust me i have 3 GPs and 2 hamsters!!
Start with letting the hamster sniff your fingers, then touch the hamster, stroke it gently then pick up slightly. Do this over a period of 1 week. Eventually, your hamster will love you!!!!! mine used to attack me, but slowly wean them on to loving you!