John Ozoga has mentioned this in a few articles in Michigan Out of Doors over the years. There are two primary separation phases that occur. The first is when the doe is getting close to estrous, with the family unit usually regrouping shortly thereafter. The second period is when the doe is ready to drop her fawns. Again, even after this there is generally a regrouping of the family unit. I've got a group of 11 does coming in pretty much every night right now. It's obvious from looking at them that there are a few generations in that group. Either that, or they are just all really good friends that always seem to be together and have a very noticeable age progression.
As was mentioned, the fawns don't really need momma for milk by now, unless it was really late born and if that's the case it doesn't have much of a chance anyway. The thing that concerns me is the social/learning aspect of the relationship. Up here in the U.P., many of these fawns need momma to show them the ropes to get through winter, where to eat, where to go to yard up, where to migrate to, etc. I think a lot of the fawns will hook up with grandma, aunts, cousins, etc, but the best teacher is momma (this is my opinion, based on LOTS of pictures of a very recognizable doe family unit (got a string of piebald deer running around) in my back yard).
That being said, I don't have an issue taking a doe, regardless of whether she is with fawns or not. Even if it is a lone doe, chances are good that she has fawns running around somewhere, so either way you're probably orphaning them. As I've witnessed and was mentioned, they still seem to make it through winter so they're learning the ropes somehow.