Fill in the blank with the correct alternative from the options given below:

She is on the look _______ for a new job.

out

The correct option to fill in the blank is "out".

The phrase "on the look out for" means "searching or actively trying to find something." In this context, "something" refers to a new job. The other options are incorrect because:

• "About" means "concerning or relating to."
• "Into" means "to or towards the inside of something."
• "Over" means "finished or ended."

Therefore, the complete sentence is: "She is on the look out for a new job."