Found it! It was GAC Toys, as I suspected but at first couldn't confirm. There appear to have been two issues with several different hair variations using the same head sculpt: GC006 and GC019. Here are some eBay links to some of these, but you can look around.
https://www.ebay.com/itm/1-6-Female-Head-sculpt-for-Blonde-HAIR-GC006D-12-figure-Phicen-Hot-Toys-USA/273815013471?hash=item3fc0a5885f:g:WPAAAOSwlJlfh5xj
https://www.ebay.com/itm/1-6-American-European-Female-Head-Blonde-Short-Hair-For-Phicen-USA-IN-STOCK/132235317698?hash=item1ec9d6d1c2:g:nfMAAOSwiQ9ZS2EB
https://www.ebay.com/itm/1-6-Scale-Model-American-European-Female-Head-Sculpt-BLONDE-F-12-Figure-Body/283431186131?hash=item41fdd0aed3:g:is0AAOSwbh9cmlhW
https://www.ebay.com/itm/GACTOYS-1-6-Female-Blond-Short-Hair-Head-Sculpt-GC006-F-12-PH-Figure-Body/184017825110?hash=item2ad8512d56:g:-r0AAOSw3k9coxVs
https://www.ebay.com/itm/1-6-GACTOYS-Female-Blond-Short-Hair-Head-Sculpt-F-12-PH-Hot-Toys-Figure-Body/223911537974?hash=item34222aed36:g:ErsAAOSwqgFeR5Vc
https://www.ebay.com/itm/GACTOYS-GC006-C-Blonde-Short-Planted-Hair-Female-Head-Carving-F-12-Figures/153437321499?hash=item23b993b91b:g:VKAAAOSwWB1Z4D1I
https://www.ebay.com/itm/GACTOYS-1-6-GC006-Short-Blond-Hair-Head-Sculpt-F-12-PH-Female-Action-Figure/324246022230?hash=item4b7e91a856:g:k7oAAOSwVVlcoxVp
https://www.ebay.com/itm/GACTOYS-GC019F-1-6-Girl-Blonde-Hair-Head-Sculpt-Model-Fit-12-Female-Body-Figure/184308356170?hash=item2ae9a2544a:g:5EsAAOSwZ~tbn0wU
https://www.ebay.com/itm/1-6-Female-Head-Sculpt-GC019-F-Blonde-Hair-For-12-PHICEN-Hot-Toys-Figure-USA/132755768651?hash=item1ee8dc454b:g:6AYAAOSwGCNbf3Ld
https://www.ebay.com/itm/1-6-Female-Head-Sculpt-Blonde-Hair-F-GC019-For-12-PHICEN-Hot-Toys-Figure-U-S-A/153148270843?hash=item23a85928fb:g:ch0AAOSwhE9bfFb9
https://www.ebay.com/itm/1-6-Female-Head-Sculpt-Long-Blonde-Hair-G-GC019-For-12-PHICEN-Hot-Toys-Figure/153148273985?epid=9028516383&hash=item23a8593541:g:lyEAAOSwjKJbfFfJ
https://www.ebay.com/itm/1-6-Female-Head-Sculpt-GC019-G-Blonde-Hair-For-12-PHICEN-Hot-Toys-Figure-USA/132755769352?epid=9028516383&hash=item1ee8dc4808:g:Q~UAAOSw0rRbf3MW
https://www.ebay.com/itm/1-6-Female-Head-Sculpt-Blonde-Hair-GC019-F-For-12-PHICEN-Hot-Toys-Figure-USA/192635053138?hash=item2cd9f1a452:g:mG0AAOSwdPZbfjxM
Edit: Crossposted with rui. You have found one of these indeed. And now that I look at it, I can see Charlize Theron in there.