Both Veronica and Christine were from the California chapter. Elijah allowed Veronica to come with him into the Mojave, while Christine stayed in the California Chapter. The BoS tasked Christine with killing Elijah. It became personal for her after he captured her in the Big Empty and preformed medical experiments on her.
You can mention Veronica to Elijah at the very end, in the vault, if you talked to Veronica after installing the DLC. He confirms his role in keeping Christine and Veronica separate.
My mistake.
You can mention Veronica to Elijah and he will remark that he's not surprised that she survived Helios One. Christine, when she's mute, will indicate that Elijah separated her from her girlfriend (she'll correct you if you say husband). When she gets a voice she again says that Elijah separated her from her lover, although she doesn't mention Veronica by name.
Since Christine is from the California chapter, and was forced to leave her girlfriend, its strongly implied, though not explicitly stated, that she and Veronica were a couple.
I'd provide links, but at the moment my internet svcks.