please help me optimised my telephone services

1st user (myself)
currently got 1 maxis line (no contract) just switch to DG smartplan 68 coz heavy use data /no calls = no problem/happy..

2nd user (my GF)
another maxis line(contract > November 2011), problem happen when this user when she need call more(data ok), especially call to friend long time (>5 hour per week) where i think is better they get 1 plan that suits them.
no problem maintaining the current maxis i think still got 1 cheaper way to do it.
her current line is Value Plus 50 + Data 500mb

i propose she sub 1 line under maxis (maybe get family plus- RM30, Get up to 15 hours of free voice and video calls between family lines, Get up to 1500 free SMS between family lines.)

or ask her fren get celcom exec and sub 1 line to her (family 1+5 = RM15)

or digi/umobile? have not survey... need help on this 1

or just ask them use viber(free call = LOL)