It is very easy to verify the existence of twins in utero:  ultrasound will
show two fetuses!  Also, blood levels of HCG (used to detect pregnancy) are
also usually higher in multiple gestations.  Depends on how far along she is.
 As for "echoing" heartbeats, I'm assuming he's just using a doppler for
this.  Yes, there can be an echo, but NOT at a different rate!  However,
sometimes mom's heartbeat can be heard at the same time, and is often slower
than the baby's.  If she's "hyper" like me, though, her heart rate
(especially if she was just told she might have twins!) could be in the 120's
range--which is also low-normal for fetuses.  At any rate, I would advise her
to talk w/her dr. about an ultrasound to clear up the situation.  If she
really is going to have twins, pretending it's "just an echo" isn't going to
make it go away, and will delay her acceptance of and preparation for a
challenging pregnancy.  I, too, agree that breastfeeding twins (especially
since she's nursed before, & has a bit of confidence & experience) is MUCH
easier than bottlefeeding.  You can't bottlefeed two babies at once, so
feeding takes up twice the time.  For those well-meaning friends & family who
say they can "help" if she bottlefeeds, point out how they can help in so
many other ways: burping, changing, rocking the babies, tending to the older
kids, housework, cooking, cleaning, errands, etc.  Breastfeeding is MUCH less
taxing than these things!

Carol