How bad is it to leave a job after 2.5 months?

I’ve been in the company as a trainee for 2 years. For the most part I did not enjoy my experience. 2.5 months ago I moved to a new team internally. I waited for this role for one year. The job description is different to what was advertised. I found out what I would actually be doing through an internal welcome email. Awks! I haven’t spoken to my new manager. She is quite passive aggressive. I’m not interested in dealing with that so I do what is asked of me to a very high quality. I will speak to her but she’s very keen to keep me in this admin/tracking role. So I’ve started looking for new jobs. Will this look bad? I won’t put it on my CV to avoid questions etc..