Yes, my little girl hated having her arms in a normal swaddle blanket and would always manage to squirm them out the top no matter how tight we wrapped it. This swaddler made it impossible for her to do that, which she quickly realized, and actually calmed her down. Hope this helps!
We live in South Texas and our child was born at the beginning of August (so, it was like 13-110). We just put him in it without anything else on, and he was happy as can be! He runs pretty hot too. Even in the winter we had him in just a onesie with the blanket on.
This can grow with her to some extent. My son is very average in length but still had plenty of room when we stopped swaddling at 3.5 months. So depending on how long you want to swaddle, she'll probably have enough room!