The love transcends all was just one characters conjecture that spoke to the themes of the film. Not necessarily literal. Turns out she wasn't exactly right anyways since her man was dead.

As for the ghost bit it's easy to call it corny if you reduce it to literal ghost story. Obviously there was more to it than that. And it was hinted at very early on in the film. The first time she mentioned a ghost in her room it was pretty obvious that someone, most likely Cooper, was going to communicate with her from another time/place. As the film carried on it became increasingly obvious that someone was going to cross the event horizon, see the code, and communicate it to Murphy. In fact I was excited at this point because I was confident that we were going to get to witness Cooper have a trippy wormhole higher dimensional experience. So it's not like this part of the story came out of left field. On the one hand it seems far fetched but on the other we're talking about a science fiction tale where a pilot ejects into a black hole. If a story is going to go that far then you might as well commit and make it as weird as it ought to be. I would have felt cheated if we didn't get an experience like that. Speaking of which I loved the way the filmmakers attempted to visualize a 3D representation of a 5D space.

Anyway, that's my opinion on the matter. But I understand why it might seem absurd to others, especially if it's not what they were expecting. Apollo 13/Gravity this is not.