Why does abigail “admit” that tituba and ruth were conjuring spirits? why is abigail afraid the others will confess what they were doing in the woods? how does abigail treat the other girls? how does she treat her uncle?

I am currently a part of a production or The Crucible right now!
She Tells the others that Tituba was at fault because she has a lower standing, since she is a servant. 
Abigail is afraid that the others will confess because if they do, she'll get in a lot of trouble for sending all these people out to hang. She will get killed if they confess. 
She treats the other girls quite terribly. She wants them to be afraid of her so she can manipulate them.
She acts different towards her uncle because he took her in. If she gets thrown out of his house then she will be homeless.

The answer to your question is a. true.