Backroads has women's groups. I know this because we are doing a Backroads family trip for my 50th this year!

Happy birthday!

Iceland horseriding tour, f.e.https://islandshestar.is/tour/the-kings-trail/

https://wildwomenexpeditions.com/

They have itineraries in many countries. The Scotland tour includes horses.

https://www.goaheadtours.com/guided-tours/scotland-for-solo-travelers?utm_source=google&utm_medium=cpc&utm_campaign=US_Search_Solo_PHM&utm_group=Scotland_Solo&utm_term=scotland%20solo%20travel&utm_content=678436004773&mt=p&utm_device=m&invsrc=g.1403&gad_source=1&gclid=EAIaIQobChMInqbrq7zjgwMVPl5HAR2uuQqNEAAYAyAAEgL1TvD_BwE&gclsrc=aw.ds

Scotland

https://www.backroads.com/trips/WELIW/cotswolds-england-womens-walking-hiking-tour

This company has tons of itineraries