She'll die. We feel awful for even saying this, but Gilly is a goner. Where is she staying during the battle? In the Winterfell crypt, which is an awful idea since it's full of dead bodies just waiting to be awoken by the Night King. Would her death be tragic? Of course — she'll probably die protecting her infant son, and her death will also destroy her boo, Samwell. Like Gendry, Gilly is known enough within the fandom that her dying would be crushing, even if she's not a main character.