Mommy's Discipline Gone Wrong

I'm a personal trainer and recently started playing with my client, let's call her Jane. We've been friends for years now and she trusts me implicitly. The dynamic works well for us, I guide her workouts but also keep an eye on her diet, lifestyle stuff too. Over time, it evolved into something more intimate. I became Mommy to her little girl. She responded so positively to my nurturing care, the discipline I imposed, like if she skipped a meal or didn't train properly, we'd have our heart-to-hearts. It felt natural, even therapeutic. Until recently. We were in a rough patch of her recovery from an injury, and she slipped up on her exercise routine. She's always been my little girl who listens but this time... I snapped. Told her off harshly, like no Mommy would ever do. Now we're both reeling. Is it normal to feel such rage when disciplining? Should I end things or can we talk through this?