I am so sorry, that must have been really hard to hear.
It is absolutely okay and valid that you are grieving what could have been. When we become parents, I think all of us have some vague idea of what we think their life (and by extension ours) will be like. And sometimes, it works out like that. Far too often though, it doesn't. So we need to adjust, we need to figure out what we need to do to minimize those challenges that we know our child is now going to face.
I have no doubt that you will take this in stride. It's very clear that you love your daughter and honestly, that's the best thing you can do. Love her for who she is and she will thrive no matter the challenges.
Plus medical science is advancing all the time. Maybe one day there will be a surgery or a technology that can help her walk independently. Remember, cochlear implants were once considered science-fiction and now they're pretty common.
Be kind to yourself. Try not to worry too much about what 'will be' and instead focus as much as you can on the present. We're all here for you and cheering you and your daughter on! You've got this.