I ride alone. I LOVE to ride alone. My friend's husband has asked her not to and she honors that. It's a personal choice. I also drive alone, hike alone, used to run and cycle alone. There are risks to getting up and stepping outside the door each morning. We each have to choose the risks that we are willing to accept.
I'm 64 years old and two years ago, while out riding alone, my own dog spooked my horse and I came off and landed so hard on my back that I had compression fractures of two vertebrae. I had my cell phone. I had a signal. I lay there on my back, talking to my husband, my daughter and the 911 dispatcher. Friendly neighborhood rural fire department folks found me easily (this part might have been much more problematic). I wish it hadn't happened, but it wasn't the end of the worlld.
I do try to let someone know where I will be riding. I was telling my husband that when the times comes, I would like to be cremated and sprinkled over the trails from horseback. He said, "I know, up the pond trail and down the clinic trail. Right?" He'd been listening.