Good luck at the evaluation! That is the very best place to start, and it's great that you're getting this and the lazy eye taken care of at such an early age. Teach her that her differences aren't a bad thing, in fact, they make her unique! Help her embrace it rather than be embarrassed by it. I had a huge gap in my 2 front teeth as a kid, and I LOVED IT!! I thought it was the cutest thing ever and I laughed when people tried to tease me, like 'you're just jealous!' I still think tooth gaps are nerdy and adorable ;)
Her problem could be something as simple as her brain is still learning to think of the word, send the message to her mouth and vocal cords, and produce the proper sound. That can be frustrating for a toddler, especially one who really tries to be independant. Lots of practice, and she'll get the hang of it :) Let her chat on the phone to grandma, grandpa, dad, neighbors, whoever... practice makes perfect!! And again, embrace it. Once she overcomes this she will be SO proud of herself (if she's even noticed it all all) and don't waste your time worrying too much about this. No matter what, she's still your little sweet thing :) Best wishes!