Fun with speech

So, dd2 has a speech evaluation next week. Dh and I both think there is nothing organically wrong with her. She just doesn't see the point. She can sign very well, and picks up new signs as fast as we can teach them now that she conquered her receptive issues. She says, "ma," "da," "ba," and "w" plus vowels. She does NOT babble. She will now say "dada" or "mama" for an adult and this week she started to imitate "bah...bee?" when we say "baby" (very, very emphasized per the usual to help her pick out the sounds). She doesn't say it on her own, but it's her first two-sound combo besides "uh-oh" so that's impressive. She also now says "mi" for milk instead of "mah." So see, she's progressing! She just doesn't see any need to use speech, really. She signs and signs and if you ask her to speak instead of sign, she just signs again and again and again and gets very frustrated and cries/screams. It is kind of nice to have a 21-month-old who can't say "no," LOL, but she can shake her head and then throw a tantrum. *sigh* We're working on the self-control stuff. She doesn't have any. But that is half the SPD and half her personality. There's nothing inhibiting her speech but her own desire or lack of. When the developmental behavioraist tries to get dd2 to talk, dd2 just stares blankly at her, so it's not just her ignoring us. She just sees no reason to use her mouth. She'll sign. That's "saying" it to her. And if she does make her sounds, she signs along with them. The vocal is just for emphasis, lol. We talk and add gestures for emphasis. She signs and adds a sound for emphasis. It's not "speech" to her.