If an animal (or person for that matter!) is "barfing" PLEASE TAKE THE FOOD AWAY! After a few hours of not "barfing" perhaps offer some boiled rice. Or-wait for the vet tomorrow. But don't just keep feeding it, unless you love cleaning up "barf" and want its electrolytes all messed up!
I am glad it is going to the vet.
And-BTW, LetAGirlShowU, for a small dog, 12 is NOT all that old. 14 and 15 is not all that uncommon. Mine old girl is 13, has had Addisons disease for 6-7 years, and noone ever guesses she is as old as she is! (not many teeth, but besides that.....good to go!)