But she didn’t want to be tracked down. She didn’t want to be kept, anywhere. “Is someone here for me?” she had gone down to the lobby in her nightgown to ask the doorman one morning. “Am I moving?” she asked my aunt. She was sensing it was time to go. Even halfway out of her mind, she seemed to recognize the truth of that. When I still couldn’t.

I never wanted her to think I’d abandoned her. I wanted her to know I was fighting for her. I kept asking what I could do to help her, what I could do to make her happier. She looked at me pityingly every time. “There’s nothing you can do, because it’s not up to you,” she would say. “You’re here with me now. That’s enough.”

Toward the end of the summer of 2009, as we stood out in her garden, she said: “It’s not like my old garden. I don’t work here much. It’s not at the front of my mind.” I said nothing. We had actually worked on it quite a bit just a few weeks before.

I walked her upstairs and offered to tuck her in for her nap. “I’m not sleeping, I have things to do,” she proclaimed. I hoped that didn’t mean making three dinners, as my father told me she recently had, but again I said nothing. Once outside the building, I looked up at her apartment, and there she was, standing on the terrace, waving. I felt buoyed by that. Often, she didn’t remember I’d been there, even a minute after I’d gone.

I love you, she mouthed. I blew her kisses and patted my heart and mouthed back, I love you. She was wearing a yellow shirt and she was smiling and her blond hair shone in the sunlight. She was so beautiful, and she beamed down at me with so much love, and I waved and she waved. And then her expression changed — ever so slightly — as she looked at me standing there waving, and she grew impatient, possibly a shade scornful, as if to say, “Enough already.”

Out of the blue, I thought of Hickory Hill, a summer camp at a country club where she was a counselor when I was 3 or 4. We were near the pool, and she had given me a dime to buy potato chips at the snack bar. I waited for her to take my hand and lead me there, but she shook her head. She wasn’t going with me. I was a big girl, and she wanted me to get in line alone. It’s O.K., she told me. I’ll be right here, watching.

I wanted no part of that experiment and was about to throw a fit, but there was something in her face — the same something I had just glimpsed — that assured me I had no choice. I was a big girl, whether I wanted to be or not. I got in line.

And that day, as I watched her on the terrace, it was she who made the decision again. I stopped waving and smiling and patting my heart. I left.