Now supervising my old boss

I work in a sports clothing chain as a weekend supervisor fri evenings and saturdays. my position is under the assistant manager, trainee manager and the store manager and my responsibilities mainly include supervising tills, shop floor staff , floor standards, training and smooth running of the store, replensihin stocks and increasing sales through suggestive selling so its a very hands on role. the thing is the assistant manager who i get along great with has just decided to go back to do a university course and has changed to a staff position on the same days i am working. Im like 18 and have been doing this 5 months, she however is 27 and has many management qualifications and years of experience. Therefore I dont know how to handle the role reversal, should i just leave her to do her own thing and jus get the other younger staff (like most are 16, 17) to do the crappy jobs or should I treat her the same as everyone else? I feel im rubbing her nose in it if i tell her to do stuff all the time like i do the others, and like i said we get on great. Help me deal with this.