2 females new owner

[Impact]

Hi again all
i got a few questions and i think u all may be my best source of help
i used to own cockateils some love birds a few budgies
and i remeber that when i owned them 1 at a time i could tame them alot easyer.
will me owning 2 female parrotlets in the same cage and they are sisters and very loving to each other make it hard for me to tame them and teach them to talk ?
they are about 15 weeks old now 1 is very gentle the other well i need a iron glove for that 1 but over the last week she aint bit me much just opens her beak.
can u advise me on the best way to intergrate with them. they may not be settled in yet they very quietly chirp and grind there beaks.
they always run back to there cage and the 1 that bites sometimgs squashes her self to the floor and opens her mouth to bite me. i move nice and slow and she will get up and walk away the funny thing is if i cup her in my hand she will hudle up and go to sleep there or bite me1 but her bite aint like an attack its like she just likes chewing my flesh. guessing shes no vegitarian haha.
any help will be appreciated
im sure i will get there with them but i think advise is the best weapon
Thanks all