Whoa! That girl in the cemetary with Modern Clara was Mels? I totally didn't pick up on that. I'll have to rewatch that one.
With regard to Clara's apparently ability to reincarnate in at least three eras (Victorian England, Modern Day, and the future (52nd century?)), I have a theory on this. I came up with it after talking to a friend of mine who is REALLY into Doctor Who history. I'm not going into go into depth into it, partially because I don't want to spoil where they are potentially going with this. However, I will say that I think it has a lot to do with the 'Great Intelligence'.
If you want to know more, check the TARDIS Wiki about the Great Intelligence. Reading up on that and the Doctor's companions during those episodes, will tell you what I think is going on here.