I'm gonna add 2 anecdotal notes on Nicole.. I saw Her at one of the Extravaganzas in the late 9os ('97 I believe). She was in the lobby of the hotel hosting the show, mingling with fans. Admittedly, She had on steep heels, but She looked gigantic. Probably around an inch or two over 6 feet, and then another 3 or 4 inches added with the heels. Really impressive..
I might have met her at the same one. She had heels on, but I'm confident her claimed height was valid. I also met Gabrielle Hames 6'1" and Shawn Tan 6'0" and can vouch for them as well. I'm 6'0", so it's easy for me to gauge women in that height range. Also met Skytriss 6'6", though she's in a different category. I didn't measure her, but she was up there somewhere.
Interesting list of tall actresses here:
http://www.imdb.com/list/ls009013498?ref_=rls_2