Why did this girl take so long to respond?

[997]

I hit on a friend of a friend on Facebook. She didn't seem interested until I tried to get involved in her charity. From there we have mostly just been friendly and met up once for coffee and a secon time at the groups meeting. It's never really gotten personal. Last week we texted about the organization but I shifted to asking her about her summer plans. We chatted for a bit then I didn't hear from her for a week.

Today she text me and told me she was sorry but forgot to respond and had been really busy. She answered my last question and asked me what I was up to this summer. What's the real reason for the delay? How should I respond. I kinda lost interest, it's obvious she isn't into me right?