If a child cannot sit up alone and unaided, propping the child up is supposed to be bad for development - I've not done research on this so cannot give an opinion. However, boredom is a great stimulant. DS had a floor mat with an arch over it (which he still loves) and quickly got the hang of baby jigsaws. DS was very frustrated just before he started crusing (didn't crawl) so maybe she really wants to move and is finding it hard? It's a great encourager. Put toys just out of her reach and she'll have a focus then.