If you both dress cooly and make sure you have plenty of ventilation and moving air as well as skin to skin contact, you should be fine. So make sure baby is right against your skin, rather than putting anything between you, as your skin will regulate her temperature to cool her (and you). If it's so hot, you're both still really uncomfortable, then I'd try to get somewhere cooler to prevent overheating, somewhere with ac, or a fan, or better ventilation. Babies are meant to sleep on their mummies, even when it's really hot, the key is just making sure you dress appropriately and aren't somewhere too stuffy. A drink with lots of ice next to you while she sleeps will help too.