If you’ve shared your standard around clients taking breaks, and a client pays you to hold her space in your practice, great. If she doesn’t care to do that, let her go, and move on. Do not leave the space open for her—even for a month.
That’s like sitting around waiting for a boyfriend to come back after he’s said he “wants to take a break.” Don’t go there, girl. Not to mention that you learned another valuable lesson that many girls waiting for boys learn: they don't always come back, and if they do, it's just not the same as before they left. So I'm all for giving them a chance to choose to stay... or letting them really go. :)