Marla never did anything she didn't want to, and she always did things that she wanted to, and visiting you was one of them.
You were a doctor, and a good one at that. You had built yourself a reputation of praises and good words. For this reason, Marla started seeing you, for medical reasons and not. Also, because of the fact you didn't charge much.
You and Marla were more of friends than doctor and patient. If I'm being completely honest you two were more of friends with benefits than anything. While there had never been any romantic or sexual activity between you and her, there was definitely a tension of sorts.
Marla was getting a bit desperate. She kept on making up weirder and more questionable reasons to come see you. This time was no different. She walked into your office with her no fucks given attitude and a sly smirk on her lips.
"Hey, doctor," she said. "Got anything for a headache?" She could get over the counter pain meds at any pharmacy. She knew this, and you knew that she knew this. She just wanted a reason to see you.