RWBY S7 Episode 5-6 Reaction

So far as we know, Maidens are not generally isolated. The original story of The Seasons implies the common practice is for Maidens to travel the world helping where they can. In Season 3, Qrow told Pyrrha their job can get more difficult if the power goes to someone random if the person last in the Maiden's thoughts at death was not a young woman. This could mean Ozpin's team left it up to chance OR tried to control the situation more over the years by removing variables (i.e. isolating them)

Amber, the Fall Maiden, was brought to Beacon and hidden in the vault as a precaution due to Cinder stealing a part of the power before Qrow stopped them.

In this instance, Ironwood is isolating Fria due to the increasing tension and unrest that started with The Fall of Beacon. It's possible he was planning to do it anyways regardless, but we don't know that.

And remember, isolating a Maiden and letting them see only a single person until they pass doesn't guarantee that person will receive the powers. All of this is just so there is a higher likelihood of them passing to the person of Ironwood's choice.

The power goes to someone random if the previous maiden thinks of "a dude or some old hag" which is why Winter is the only person Fria's allowed to see. Amber (the previous fall maiden) was wandering freely before she was attacked and kept underground on life support. The previous spring maiden ran away from Haven, freely, before she was picked up by the Branwen tribe and then killed by Raven (the current, and currently free to wander, spring maiden). It's assumed that when at the end of a natural life, the maidens are THEN isolated with only the person who's going to be the inheritor of the power. The other two times we know of maiden power transferring is through force, and the assailant was the inheritor. And the fall maiden was an especially rare case, since the power was split and forcefully taken (the chain of events in volume three w/ pyrrah and cinder and everything)