I looked at the 1861 census and it indicates Ellen was married at the time. If this is correct, then perhaps her husband George was serving in the army somewhere.
Sometimes boarders were actually relatives. I'd like to suggest, if you haven't done this, to trace the family that Ellen was boarding with. Maybe they are her relatives--or her husband's.
Also don't rule out that her maiden name could have been Bambury too.
I hope this is helpful. Good luck.