"I'm heading there when we're done here, we can walk over together." She'd been considering inviting Alphonse for the stroll anyway. "It's a pleasant evening for a walk outside."

And there's always the chance the haunted house will actually have some frightening things in it. She doubts either of them want to walk anywhere alone after, if that turns out to be the case. This way it saved either of them having to ask the other after.