In a way, she was. He'd have to take care of her now as he fought to take down Lucas quietly. Having her stay with him - especially if others heard of it - would lead to gossip and people being suspicious. He liked being Xavier in his own way and hadn't planned on abandoning the identity. It was his most fleshed out after his Evan one. He couldn't return to being Evan thanks to fleeing the states and he couldn't be Edward again either as he was dead.
But he wasn't about to leave her to fend for herself. He was better than that - she'd suffered enough for her mistakes. "You won't be," he lied.