Junior confrontation

I have a junior staff member who is seriously pushing my buttons. Works to the minute of her 40 hours per week less 2 minutes to 15 minutes each day. And I just can’t let this go. 30 years in business and this girl had me shaking after confrontation with her this afternoon when she left at 4.55pm, insisting the time was 5pm. And this after arriving at 8.35am – 5 minutes late. My time, paying someone for time I can never re-coop. Stealing my time. Ingratitude. Undeserved entitlement. 9 other staff who turn up and love their work and give way more than their 40 hours each week. (ps staff are all watching this drama)

Really struggling with this one. Where does the line get drawn? Control over another person vs expectation of a staff member.

I had already done a CTFAR in anticipation of this confrontation.
C = she arrives late
T = Traffic again, she’s young, learning her way
F = understanding
A = Discussion about adult behaviour around responsibility and accountability
R = respect on both sides. Working well together
However, when I started the calm conversation about leaving early, I ended up apparently being the aggressor boss! How dare I question her, of course she would never take any extra time.
Appreciate your assistance with this.