IM CONFUSED! BUDGIE HELP!?

ok so i have 2 budgie females. 1 baby and 1 adult. my baby is hand trained when i got her and sits on my shoulder and will sometimes eat out of my hand and steps up on my finger. my other one wont do anything but go on my finger and try to bite me and lean back and get away. my baby trained one does it too. but she lets me do all of this. she still bites though and tries to fly away. what im saying is that my trained baby is afraid but not afraid. and when i put budgie noise on they both love it and get all cosy and sleep. they chirp too. btu when its off they are dead silenced and afraid. i cant keep the budgie noises going all day, but i want them to feel comfortable. by the way i have owned them for 2 months. also fresh food and water EVERYDAY!