Until reading this post I had no idea what age you were but assumed teens or 20s given the ridiculous idea that any grown up woman and functioning human being would have a problem with such a harmlessly benign hobby as pointing a camera at ships.
You may need to give this woman more credit than you are. I'd like to think that anyone, her included, over the age of say 25 would have enough maturity, nous and intellect to not bat an eyelid over your chosen hobby.
Another way to look at it would be to ask yourself how much less lonely would you actually feel if you were constantly trying to act like somebody that you're not? First it might be abandonment of a hobby, next week it might be changing how you dress, the week after it might be the giving up of friends who she doesn't like or who you think she wouldn't like and on it could go until you have nothing left that is fundamentally you.
But in all seriousness, I can't imagine for a second that ship photography would even be a problem.