I think it is so hard to find ways to meet the needs of kids whose subscores are uneven. Here's some thoughts on your questions:
Instead of focusing more on either math or areas she is already excelling in, I would recommend meeting her where she is in both. Sounds like she is still at grade level for math, so it's more about enhancing her learning in all areas.
For her IQ, I would not use either one, but both. Have demands and expectations based on her subscores instead of the total score.
I assume the GATE program is a gifted program, it seems like the real advantage is not enhanced learning, but getting the social support and being around other children who think similarly.
For acceleration, I assume your daughter is pretty young for her grade already. When my kids school wanted to accelerate my daughter, I started asking numerous teachers what they thought. Interestingly, I found that every elementary school teacher (from numerous states) ALL recommended accelerating her, while EVERY middle school/high school teacher recommended against it. They all said that while socially/emotionally it wouldn't matter now (kindergarten), she would be "eaten alive" socially in the older grades. So I would recommend also looking down the road as well.
I have no experience with half days at school, but I do know that kids thrive with consistency, and I would be worried how your daughter would feel being pulled out of school halfway through and not having the same experiences as the rest of her class. I have considered going to the school and taking my daughter to the library to teach her myself, that way she would still get to do the other subjects and school events with everyone.
Good luck, those are difficult decisions to make.
