I'm concerned that if I don't buy D new stuff, that W will bad mouth me to D and/or not let me speak to her after the move.
I hate to say this, but I don't believe those are related at all. W is already showing you the respect she feels toward you in how she is presenting you to her friends and family. Why would D be any different, especially after she starts talking about how much she misses you? Don't be held hostage, here. If you do go down this road, make it clear that you still want to be part of her life. Get some kind of agreement.
It's worth noting that even though you aren't a legal step parent, you MAY actually have some rights here (YMMV, don't know about Colorado). If you feel like you want to continue your relationship with D, it would probably make the most sense to dig into this before they leave Colorado.
