 She was taken in as a child so she grows up knowing Hellboy, they eventually become more and both films touch on them working out feeling for each other as well as how their relationship would work with who they both are.The 2nd film has Liz dealing with being pregnant with Hellboy's twin children and how that will change their relationship going forward as their lives change due to other plot points.However, in the comic books Liz and Hellboy are only friends.