No way she is that tall. Heels must be adding atleast 4". I met Karen Gillian once at a comic con and I remember her being a few inches shorter than me. Ive heard actors fudge the numbers on this stuff on occasion.
They all could be fudging the numbers for all I know. The heels on her Nebula boots do look to be adding about 4", but it's really about how we perceive her relative height on-screen. I think she comes off as tall & quite leggy compared to her counterparts. Your mileage may vary, but as long as we're both happy with the figure in our respective displays that's what matters.