Lydia is fine,but as time flows.I got tired of her "I will carry the burdern for you".Besides,when I hit the cellar of Longhouse,the first person got in my eyes was Ria(a really cute girl always saying"I killed a bear yesterday,have you killed anything yet?")and i fell in love with her once at the moment.So I consider replace Lydia with RIa(after you become harbinger of the Companion,you can take anyone who you like in the Companion),but then,the problem occurs.While we are doing something bad at Windhelm's stable,it occurs to me that I wana finish so job for the thief guild, then,I took the carrige to the Riften,but guess what,Ria didn't jump in! I tested many times,both with fast travel and carriges,but it is apprently that Ria want just spend the time with me running thorugh Skyrim.By the way,Lydia is okay,her didn't care about fast travel or carrige,always stand aside me,I think it is may be that she is my housecarl,that's her duty. I did't test anyone else,cause Ria is my favourite. Have anyone faced the same issue? Any sugeestion to "fix" this problem? or any mod? Ria and I shall give you our best gratitude.

bump

try using wait to see if she pops up but I never had this problem with her or anyone