I can relate to your hesitancy to share a cabin with a stranger. One bad experience made me vow never to do that again; however, in all fairness, I have heard of more positive experiences than negative. Some cabin mates become friends and plan future cruises together. If you really, really want to go on a singles cruise and do not want the expense of having your own cabin then give it a try; otherwise, save up till you can afford it. It all depends on how badly you want to cruise.
As for cruising being a "couples" experience, I think you will find more singles on a short cruise, especially if it's a holiday cruise. I also recommend Crystal Cruises for anyone traveling solo. Pricy, but well worth it, and great for singles.
How about other singles on this message board? Can you give this person some tips/advice based on your cruising experiences?