Hey, solo woman cross country tourist here - go for it, it's fine!
Pepper Spray - yeah, Halt for dogs & bad men, I never used mine but it's lightweight peace of mind. I used a small one, in holster on your handlebar.
Lock - yes, one medium weight cable lock long enough to go around a tree or fence or whatever. I like combo locks, because you can't lose the key. No one but you knows your bike is fancy/expensive/hard to fence, if it gets stolen it's not because it is recognized as valuable, it's because it's easy to steal. It's not hard to fence, by the way, any meth-head would be happy to sell it for $20. So make it hard to just walk away with, but understand that any lock can be broken. If worrying about it is going to ruin your trip, use a different bike.
Photo/Netbook - less weight is really better. If you can manage to not take a computer, that's much better. I had to take one on a tour (for work) and it was pretty annoying, even though it was a really light one. Every gadget you bring probably has a couple of accessories, the weight really starts to add up. Try to minimize.
Water filter - no. Bring a small jar of iodine tablets, the number of times you need this is so small it's not worth the weight. Carry 3 bike water bottles and if you are heading out into somewhere you know will have a long way before you can get water, just buy a couple of liter water bottles or Gatorades at a convenience store or whatever, and stick them in a pannier. You can recycle the bottles later when you don't need them, or refill / carry empties.
Food - very personal, I carry a small backpacking stove & cooking gear, mostly because I can't live with out my morning coffee. I never use backbacking food though - just shop in grocery stores. cous cous, pasta, pb&j, tuna sandwiches, fruit, crackers, bagels, cheese, salami. I don't do much really fancy dinner cooking, mostly a grain and throw in some veggies or meat or cheese.
Things that I wished i brought, I bought. things that I wished I hadn't brought, I mailed home. So either way, it's not a big deal.
Have a great trip!!