Should I read anything into my girlfriend wanting our photo kept off my public page?

I showed my girlfriend the photo I wanted to post from our weekend away. She liked it, then asked me not to put it on my public page. I said, "Are we still keeping this quiet?" She looked genuinely surprised.

We've been together eight months. I've met her family, her friends know we're a couple, and she introduces me as her girlfriend. She rarely posts photos of herself. I post fairly often, including friends and family, and this was the first picture of us I had wanted to share.

She says she doesn't like being visible to people she doesn't know. I hear that, but I had imagined the photo as a small happy announcement. I haven't posted it. What stung was realising that an announcement I thought was about both of us could be something only I wanted.

How do I talk about wanting to be acknowledged without treating permission to post a photograph as proof of love?