mind to share ur gf pics.so we can help u (no pict no talk)

try to look at normal bra brand they should have more size. Dont look at sports brand.
My gf also have the same problem.

Why everyone asking his gf to lose weight? or not do jogging? he only said she has big breasts and need recs for sports bras. Big boobs does not mean fat. Big boobs does not mean a woman is invalid and cannot do jogging (or such activities).

Reebok, Nike etc sports bras are more like shelf bras i.e. no real support and give the uniboob effect. In the past I've used this but only for weight training definitely not for running.

The best one I got for high impact stuff is from M&S. They probably go up to larger sizes. I know that they have up to D cup but you have to check if they have DD or E or your gf size. They also have a few "levels" of support for different activities. Check them out. They're about RM 100.

for high impact sports like running, it's best to wear sports bra.
regular bras with elastic straps may caused breasts to sag.....too much of "bouncing" i think.
look for sports bra with hooks.
u can read more in many websites on sports bra...types, sizes etc.
just google them.

for large sizes, u can try to find in Marks & Spencer.
they have sizes up to DD cup.
ask the sales assistant to measure ur gf's size.
that's where i got mine.

i heard triumph also has sports bra.

good luck 

TS, ask yr gf to try wacoal or triumph. They have good sports bra for all sizes and quality ones too