aWWW bles the little lady.
If she is settled withe others i would not take her right away but if you have a little paddock or suchlike that she could go in but still inetract with the others that would be suitable. I would not up her food make any big changes to her diet as this could be detrimental to foalie and mare at such a late stage. Make her comfortable with as little stress as possible.
When she gets closer, the milk vein under her belly will be more pronounced, as she get closer she ll bag up and show wax on the ends of her teats, also her muscles son her haunches (down the sides of her tail) will relax and become more flaccid in preparation.
Saying that though some mares show wx or could run mlk and still take weeks, so also look for similar signs as sheep, restlessness, getting up and down, pawing etc.
i hope she lll be ok xxx