It would be best for her to do it privately on her chaise lounge next to you , not in a group. Women don't walk around topless on the main beach
It sounds like she's too shy for the A/N beach, which requires full nudity,
What WandA said. There isn't an area on the beach where topless women congregate. If she's looking to sun with less clothing amongst like attired people I suggest you try the AN beach together. Read the postings on the AU NATUREL board. Agree to give AN a try for 30 minutes then decide if you're both still comfortable or if you want to return to the textile side of the beach. Do it on your first day so if you like it you don't regret not having tried it sooner.. You both may be surprised.