Open Adoption Quandary

When do I start freaking out that C has not gotten back to me to schedule our next get together? 

Let me back up.  Ever since we were placed with Baby X, we have met with C every 2 months on the dot.  Without fail.  Recently, she's started coming to our house for these visits, occasionally bringing her mom with her.  We fell into a pretty easy routine of communication via text (her preferred mode), and e-mails with pictures (that she very rarely responds to).

Over the summer we went through our failed match, and during that time felt the need to reveal to C that we are adopting again.  We hadn't yet because we were so far away from a match (so we thought), but the birth of Baby A coincided with Baby X's birthday and kind of screwed up our schedule.  She didn't react much when we told her about the impending match, and then that it fell through.  I'm not pretending to even know what could have been going through her mind, hearing that someone made a choice that she would have made if she had support and resources to parent.

Anyway, we managed to see her one time after the match fell through, and then our summer got insanely busy with travel and vacation and various other scheduled stuff, plus C had a major life-change.  Now that she's settled into her new routine and our schedule has opened up, I've been trying to set up a get together.

For a month, I've been trying.  Before Labor Day weekend, she texted me and said she was ready to see Baby X, so I gave her all the available times on our end.  No response.  On Labor Day weekend, I sent a text asking if she wanted to get together.  No response.

This isn't like her not to respond to texts, especially where seeing Baby X is concerned.  Our problem though, is that our only good mode of communication is via text, and if she doesn't respond, how many times do I bug her?  I know she might be overwhelmed still, even if she thought she had gotten into a routine, but a small part of me worries that something happened. (pessimism is standing-operating-procedure in my world)

I feel like I'm in a weird bubble where if something indeed happened to C, we wouldn't know about it.  Her family doesn't communicate with us, although her mom is pleasant enough when she visits with C.  C talks about Baby X with her friends, but we've never met those friends.  It's probably nothing, and she's probably still figuring out to navigate her next phase of life, and I don't doubt that she's swamped.  I am forcing myself not to text until at least this weekend if I don't hear from her.  I don't want to be a nag, but at the same time I want to see her and catch up.  Plus, as it always happens, weekends are filling up with activities again.  It's hard to keep some free time in mind, when I don't know when I'll need it.