the meaning of this sentence

Context: MC can't believe that his favorite character in the mobile game , which he has been playing,is real .He is going to buy a new smartphone in a smartphone shop , to replace his broken one and participate in a gacha event . Then he saw a cosplayer inside the shop ,which is really looked like her ,and he thought that's just a cosplayer working in the smartphone shop ,which he went in to buy a new phone

"もしかして、なりきってる残念な……じゃなくて本物のレイヤーか？" Much thanks if anyone can explain to me the meaning of this sentence, and some grammar being used here o/

More context below: MC「ほ、ほんとにリリアさん？」

Lilia「ちょうどマスターのスマホが壊れて、このままもうゲームをプレイしてくれないと思ったから……」(his favorite character in a mobile game (gacha?)

まだ話してもいないのに壊れたスマホの事を知っているとはっ！

もしかして、なりきってる残念な……じゃなくて本物のレイヤーか？ (my guess but not sure based on context "If she's not her then it's unfortunate .... Then she's a cosplayer ?" )

その時、リリア（仮）さんが『マスター、まだ信じてないの？』とつぶやくと……

リリアの体が白く輝き、展示台の上にあるスマホの画面に吸い込まれたっ！

MC「Ｏ・Ｍ・Ｇ！」

吸い込まれたスマホに近づき画面を覗き込むと、その中に表示されているリリアが俺に向かって手を振っていた。