If someone pitches a fit, just tell them that if they don't like it, they can look the other way. You are absolutely not to big to ride a horse, especially one as sturdy as your mare. If she thought you were too heavy, she would have let you know and you would be able to tell pretty easily. And trust me, you won't hurt her. She is a nice solid little horse and should be able to carry you and your daughter both with no trouble.
As for the saddle, I would probably look for something that was comfortable for you, regardless of the size. However, if you aren't planning to ride for a while, you might go ahead and get a 17", it might be a little more motivation to keep doing the wonderful job you are at dropping the weight. In all honesty, you should be able to ride her within just a few weeks of when she foals. You can start out in the paddock with the foal loose and after the foal learns to lead really well, you can pony the baby out on the trail. That is hard to do for people like me and Kevin that need working horses but for someone who is just interested in riding for the fun of riding, that would be fine. You would just have to be careful about strange horses getting close and not going too far or too fast for the little one though.
EDIT: I nearly forgot about the first post LOL. I did the color calculator thing with all the information available to me and this is what it came up with.
Bay Dun Tobiano
Red Dun Tobiano
Little filly does not have any white on her that I have seen, so she's not a paint/tobiano. She's brown with a black mane and tail, but around her eyes and muzzle, she's grayish, leaving me to believe she may have defied the odds and be a grulla? I'll post pics tonight...