Hi All,
As I sit here taking a break from sick kids and hubby, I thought I might
offer some personal experience with this one.
When my youngest (soon to be middle child) was and infant I had to pump for a
LONG time.  I had the same thing happen.  Right breast would let down almost
immediately and left would take at least 5 minutes to do anything.  I never
switched to single pumping (unitl baby went back to right breast, but left
breast was still unusable for direct BF) and just sat there for the extra
time, giving the right breast some extra stimulation while the left side did
its thing.  I don't know why they acted like that, but maybe it is because
every breast is different, and they react differently to stimulation.  Just
because they are on the same woman, doesn't mean they are the same.  I admit,
it was a bit of a pain, and rather odd to me at the time, but I just did what
I needed to do, and didn't worry about it.  I had one heck of a milk supply
(so much so that I donated just over 8 gal in two months to a milk bank for
research) so was not concerned.
Hopefully this mom is not concerned, but if she is, I would tell her to
relax, and not worry about it.  SHe seems to be getting plenty of milk, her
breasts just have their own individual personalities.  :)

Take care!
Jay