Of course you can use a cutting board as a cheese board! I’m not sure that there are any technical differences between a piece of wood being sold as a cheese board and one being sold as a cutting board. Your friends are going to be cutting cheese on that board, right?
Perhaps, your girlfriend just doesn’t like the look of your cutting board? Are you maintaining it properly?
You should never soak your cutting board (or any wooden utensils for that matter) or they will begin to warp and crack. Every few months you should also oil the board with a food-grade mineral oil. Something like this should do.