What works best in a situation like this depends a lot on you and your horses personalities. Is your mare always a little jumpy, sensitive and hot, or is she usually level-headed and a slow reactor? Are you a cautious rider, or a rough and tumble one who isn't afraid of being jostled a bit?
My mare acts like every new trail is a completely alien world and stares and snorts at everything when we ride solo. She's a hot and sensitive arab, and I'm a bolder rider, so I usually just ignore the show and ride along. As she gets used to the new routes she calms down a little, but never stops looking and snorting--it's just her personality.
Someone who is less confident riding forward in this situation can always walk the horse on the trail in-hand, because this removes the anxiety of falling off. Most horses will eventually get used to going out solo if their rider has consistent confidence.