Like others I too have hiked the Pennine Way alone. Apart from bad weather, midges at Alston and being charged by a herd of cows near Bellingham, who verred off away from me in the last few seconds, its an enjoyable walk and its demanding enough! I found camping and shopping easy to do en route, including wild camping as well. I gave some thought to personal security recently and bought a 3 pack x 130db personal alarms (from Amazon about £12, light as a feather) which I thought might come in useful. Each alarm has a small rod pushed into its side, when the rod is pulled out, loads of noise!!!!!!. Easy to stop just put the rod back in. The only extra I needed to buy was some fishing line, no weight at all, £4 for 40 yards. I tried out one alarm last week in France> I was on a site with only 3 tents around. I tied an alarm to my tent entrance and then went for a meal. If I was burgled at least the alarm would go off and the other tenters and the motor caravaneers would hear it.
When I next wild camp I now have the option of using the fishing line to secure all of my area if I want to. I can circle myself if need be and if anyone, or an animal crosses into my enclosed area I would hear them before they got to my tent, maybe the 130db's would scare them off as well? I've had the experience of pigs trying to get in my tent with me and cattle appearing in the night so I know these little surprises can happen.
During my hiking years I have met quite a few lone female hikers, young, middle aged and older. None of them, to my knowledge had problems because of their gender. Once on the Pennine Way I met a young woman, she looked about 20-25 going south and the second time a couple of years later I met a young woman about 30 and we climbed over the top of Pen Y Fan together and both camped the night on the Horton campsite. My most memorable was a young 22 year old (she told me, spoke perfect English) French woman who was hiking alone in the Pyrenees. We were in the middle of nowhere by the side of a lake and she opened her rucksack to show me her machete in a very nice leather scabbard. Her Dad bought it as a birthday present, I thought, what a nice man!!