I'm sorry, but you don't lose 4 under bust inches after a surgery to gain 3 over bust inches. And "volumetry" wise, 650cc is not enough to go from D to G.
To go from D to G you need approximately 850CC base volume, that's excluding tissue displacement and compression and implant compression when under the muscle. Considering the compression and displacement you need around 1000cc to go from D to G for an approximate 20% discrepancy; which is to be expected in normal cases.
And that's not even explaining the under bust number change unless she had one of a hell of a liposuction.
Which in conclusion means she has a net loss of 1 inch bust size.
Methodology:
1. D to G equals a 3 inch gain or 7,41 centimetre.
2. Volume gain from implant is ((4/3)πr3)/2 or 852,145CC
3. With tissue displacement and compression plus implant compression from the muscle correction you get about 1022,57CC