What's the cue they give you to indicate that they don't like the 1 tog bag? Can you try to use togged sleep suit instead? I think 2.5 tog is way too thick in this weather even with nothing underneath.
They’ve expensive but we’ve switched the bamboo sleepsuit as it feels heavier for her (more like the 2.5) but is suitable for hot rooms
Minimise what she wears under it to a short sleeved vest or just a nappy.