leg bars are single combed. she doesn't look single combed?
pea comb and O gene for colored eggs are very closely linked in most of U.S. stock. there are stocks where this link has been broken- O gene 'ditched' the pea comb gene and hooked up with single comb... birds like this were used in legbar breedings.
in the long term you may find out if her gene for colored eggs is linked with pea comb- if you breed her with single comb and all pea combed daughters/granddaughters lay colored and none of the single combed ones do... that would rule out legbar and go back to EE stock.
EE mixes are rather common, there always was occasional postings on BYC asking about crossing EE with breed X, including polish. so this is kinda the more likely answer for the time being.. until legbars are more common and we can be sure they will mix with other breeds more frequently.
Legbars also give the chance to breed them into different breeds or personal project lines if pea comb is not desired...