Now THAT could be an interesting storyline, if Lindsey got pregnant, lol. But if Kay's busy, then I don't see it happening...
If you think about it, Catherine and Lindsey are a lot alike. Catherine had a rough time becoming an adult (stripping/the innuendo of using drugs, etc.) and Lindsey has had a rough time becoming a teenager (rebelling, losing her father, getting kidnapped). I think that they have become closer, it's just not shown that often. The scene in Art Imitates Life indicated that, at least IMO.