@Julia

I had been in a similar situation of working with a boss from hell. She’s exactly like the way you have described ‘S’.

My advice would be –
1. Concentrate on your work, improve your skills, go out of your given responsibilities and take on extra.
a. You will be happy giving 101% at work.
b. Your skill set will improve.
c. Others will witness your dedication and hard-work towards your job, along with your bosses.

2. Aim for your goal Graduate-School.
a. Phase out everything else.
b. You are there to work and improve professionally, do that.

3. Regarding ‘S’ criticism or pulling you down.
a. Agree with others above, that ‘S’ is a disturbed soul.
b. Do your given job, beforehand or on time.
c. Never give any excuses, for work undone.
d. Also, do not speak about your concern with ‘S’ criticism to ‘J’ or anybody at work, it will backfire.
e. Ask loads of questions to ‘S’, how to do an assigned – job, this will boot there ego.
f. Give ‘S’ the faith that they only can teach you. ‘S’ is craving for attention and recognition, give them that.

You are young and you are there to learn. Learn, ask questions, observe everybody at work, especially ‘S’ and ‘J’. Whenever you are working with either of them, observe there style of working, how they like a job well done and follow-suit. People will talk/gossip about you, but don’t participate or pay any heed to that.

Hope this will help.