In my opinion, and I could be wrong, your therapist is making a mistake by creating an expectation she's unlikely to meet.

To me it sounds like your therapist has good intentions and when she gets deeply involved in her vacation she loses sight of those intentions. I understand this because I am exactly the same way. People want to stay connected to me and I used to say things like I'd send a card and then I wouldn't and people would be hurt. The thing is, I don't ever lose that feeling of connection and if someone sends me a card it doesn't make the connection any deeper. I suppose I project my crap onto other people and expect them to feel connected to me if I'm gone. But they don't and it's led to problems.

So, now, when they ask me to stay in touch when I'm away, I say no. I might do it, but I say to not expect it. That's stopped the problems. People would still like to hear from me, but they're not feeling dashed to bits when they don't because I didn't make a false promise out of good intentions that I wasn't capable of following through on.

The mistake your therapist is making is raising your expectations. I think it's okay to talk to her about that.

Once our expectations get rationally raised -- and it is rational to hope to hear from her when she said she'll send a card -- it's normal for us to feel great frustration and disappointment when our expectation gets dashed.

To me, that's the real problem here ... not that you're demanding too much or overly needful or whatever -- but that she's given you reason to have an expectation and she's not following through. It's almost as if she's failing to show up for an agreed upon appointment because she got too busy.

If I were in your shoes, that's what I'd be talking to her about. Does she realize that she's provided you with a reasonable expectation of hearing from her? When you don't, you experience normal feelings of waiting, longing, disappointment and it's causing you to waste precious emotional energy in a way that's not helpful? And is there a solution the two of you can work on for the future?