Milk with breast milk?

I'm just wondering...
DD2 is still nursing and still going strong. She's just about 16 months
now - wow, does time fly or what??
She currently nurses first thing in the morning, just before breakfast,
sometimes will nurse before her nap (often, though, she'll only go for a
couple minutes before nap and will nurse longer when she wakes up for her
nap), just before supper and then again at bed time. She sleeps through the
night and it's rare she'll wake up at night once she's down. She'll usually
go right back to sleep on her own within a few minutes if she does happen to
get up, and it's now only once in a blue moon that I'll bring her to bed
with us, and she nurses again and goes to sleep.
During the day, she will drink juice - I normally water it down - or water.
I have yet to give her cow's milk - she has been having milk in something
like oatmeal in the morning or if I make a soup with milk, she eats that and
has for a looong time now.
So, now, I am wondering... Does she need regular homo milk? With how she
nurses, would she be getting enough milk for her age? Obviously it's
impossible to tell how much breast milk she actually consumes as I have
never pumped (couldn't pump at all, actually) and well, I know it's really
impossible to tell how much a breastfed baby can get out of a breast, even
if a person does pump.

I'm just wondering if she's getting enough milk or not, or if she should be
drinking cow's milk. She pretty much refused a bottle right from day 1 and
has only had a boob. She won't take a bottle - wouldn't even dare to try
and offer her one at this age anyways - but drinks fine out of one of those
reusable 'juice boxes' - the rubbermaid ones with a straw or a regular cup
with help. I really don't know if she should be having regular milk along
with nursing still. She seems to have plenty of wet diapers, although I
think that's partly because of the water or juice she takes. I find that if
she doesn't have much water/juice in a day, she doesn't have very many wet
diapers. Her weight gain is good and so is her growth. She seems to be
picking little words up (mom, dad, bye, hi, uh-oh, etc) and seem to be just
fine.

Any words of advice, oh wise ones?