re: the one- or two-ballerina tradition for SWAN LAKE and its Odette & Odile roles, the latter, two-ballerina variant comes subsequent to the1877 start of SL history, and then only on rather isolated occasions..
Beaumont says a second Grosky production, in 1920, following one from '01 where he used one ballerina for O/O, initially Adelna Giuri, split the roles for two different dancers.
It's for the '20 prod. that Beaumont writes: "Originally, it was intended that both Odette and Odile should wear large swan's wings which the dancers would agitate while dancing, but these were found impractical and discarded after a dress rehearsal." sketches Dyachkov of costumes with wings in Demidov, annotated as showing Odette in the second act, and Odile in both the SECOND! and third acts, are a puzzle, while Odile slated for the second act (as background figure with Rothbart?) is in costuming colored in reds, blacks, and greens, for the third act she's in a low waisted chemise of green and rose with white swan wings and medieval headdress topped by coronet. Odette for the second act is in all white, with similar wings and with a large emerald on her bodice and smaller ones around her waist. with evident intentions for putting both Odette and Odile in the second act, two ballerinas would be required. Beaumont reports that for this staging Gorsky cast the newly graduated E. M. Ilushenko, while the more seasoned and well known M. P. Reisen danced Odile.
then, o'course, there was Vaganova's 'updated' '34 staging, but essentially O/O was a one ballerina role.
the first performances in the America, on a 1911 tour led by Mordkin and Geltser had Geltser dancing O/O at some performances and Julie Sedova at others.
regardless, whether given by the same ballerina dancing Odette, or a separate one, Odile is rarely pictured in archival illustrations.
as for solo roles in the ballet, certainly these are not as plentiful as pictures of ballerinas costumed for Odette, but photos of the divertissement dancers, and even of random soloist swan maidens - i have some of these, Alexandra Baldina, for ex. among others - exist in limited numbers.