Hi Danigurl07 and welcome to TCS!
Have you brought these two indoors? If you haven't, you should if this is at all possible. The best solution would be if you could confine them together somehow since they are close, preferably in the same room, but confined within that room. I use extra-large dog crates for this and have found that they come in very handy even after the delivery - you never know when you might need to confine a pet. If you find you don't need them, you can always sell them. They are relatively inexpensive at Wal-Mart, I bought my extra-large one there for less than $60 I think ... but even the size down from that would be ok and I think it is less than $40. This would still allow these two girls to be together.
The colostrum doesn't normally come in until after delivery, however, it isn't a good idea to let the kittens you have now nurse from the 2nd Mommy.
Also, just a little reminder ... both of these girls can get pregnant again in a very short time after they have their babies. You must not let either of them go back outside again at all until you have both of them spayed. You can safely do this after the kittens are all completely weaned, probably somewhere around their 8 to 10 weeks birthdate. Additionally, outside can be a dangerous place ... the possibility of something bad happening and preventing these little girls to properly care for their babies is very high. There are also deadly diseases out there which they can bring inside to the kittens. Just so you know ...