The 23-year-old from Florida shot a seven-under-par 65 at Golf Gerre Losone in Ticino to join Artis at 11 under par overall.
South African Ashleigh Simon is one shot back after a 66 with Marjet van der Graaff of Holland a further shot behind.
Artis, whose 70 on Saturday contained two birdies and no bogeys, said: "I played solid out there again. The wind was up again so it wasn't playing easy, but I just got it around the golf course.
"I missed a couple of fairways and followed on with missed greens but managed to make a couple of good up-and-downs so I kept the momentum going and it was bogey-free out there so I'm pretty happy with that.
"I was able to control my nerves early, really. I've been doing a lot of work back home with a psychologist, Noel Blundell, and it's really helped me. I've always been someone to get a little nervous so I was able to really put into action some of the stuff he's told me and really play well."