Workout and Wandering Hands

So here I am, your typical personal trainer, single and content with my lifestyle. Or so I thought until last week when one of my regular clients, let's call her Dana, started getting a bit too friendly after our sessions. It wasn't just the lingering touches or the way she'd whisper compliments in my ear, it was how she’d invite me over for 'special' workouts at her place. Obviously, I didn’t accept. But now every time we meet, there’s an undercurrent of tension that feels both thrilling and uncomfortable. Is this some sort of boundary-testing behavior, or am I reading too much into a client's admiration? It's not like I’m inexperienced, but this is new territory for me professionally. Any thoughts on how to handle it without crossing any lines?