I assume you want a solution besides the one I’m inclined to recommend… (AKA screaming into the phone, “Are you serious? Do you know how hard it was to find this candidate?”)
This situation calls for two classic closes, whichever resonates for you. You shouldn’t need both.
REDUCE TO ABSURDITIES: First you show empathy. I understand that even though you changed the hours, they are your hours, you run your shop as you’d like, etc. It is easy to take an emotional stance, let me suggest something. Most studies show that in the typical 8-hour day an employee is truly “working” about half that time. And we all know there are people who can do 8 hours of work in 4 and people who take 8 hours to do the work that can be done in 2 hours. There are 480 minutes in a day, 96000 hours in a calendar year of working. Instead of looking at the number “30 minutes”, I think we should consider that she is really asking for 6.5% of the 480 minute day. (6000 of the 96000 she will work for you this year.) Isn’t it reasonable to believe that if she is as good as we both think she is, she can re coup that 6.5% in the course of a day? (and here I might offer to extend the guarantee 30 days)
THE OBJECTION IS THE REASON FOR BUYING: Can we take a pause here and give her some credit for being upfront about this? In my experience clients often complain that candidates begin coming in late, using the “Kid” excuse and making you feel bad for expecting them to be on time. She feels she can make up for this time by being heads down, no nonsense. It is BECAUSE she feels unconcerned about additional pressure to perform given the 30-minute headwind her day care creates, BECAUSE she feels her references (offer to call them and ask this specific question) will back up that she hits the ground running and is effective that we should give her the benefit of the doubt, not start the search from scratch and cut her this minor slack. (And I’d find a way to again, gently remind them that they have some culpability here by changing the time. She didn’t manipulate this, they did.)
By the way, don’t be afraid to ask if they had some bad experience in the past with some employee who took advantage of the stated hours. And if they say yes, remind them it isn’t fair to punish her for the sins of others. (And again, extending the guarantee at the end of your argument could close this up.) Be strong and SUGGEST the outcome you want.
Sigh. In this day and age, where good candidates are so hard to find, some clients are cray cray…!