84 blocks/units -
possible layouts - 9x9 - which would use 81 blocks -
if your blocks will be 5.5 inches finished size (1/2 inch seam allowances) - that will be approximately 49.5 x 49.5 inches finished (think 50 x 50 because the outside fringe/rag will probably lay kind of flat)
Another layout - 8 blocks wide by 10 blocks long - would use 80 blocks/square/units
5.5 inch "finished" size - this would end up being approximately 44 inches wide by 55 inches long.
Your daughter is 65 inches long/tall.