Problem with the manager at work,please advice course of action?

Have been working in my job X 6 yrsnow, been very responsible, great evaluations,union job,etc.
I generally love my job eventhough I work with another employee who is neither friendly or accepting of me but try to ignore her and for the most part worked fine for me so far.
This past week my manager gave me a strange assignment, to cover another area, eventhough my dept seemed busy and there was another employee (per diem) who floated there for help.
I stopped briefly by the manager's office that morning just to check whether she made a mistake and she assured me that needed me in the other area.
Now on Tuesdays and Wednesdays I float wherever they need me, but on Monday (the day I was floated) I have my own service.
On Wednesday, my float day, I floated again in another area, but I found out that they had 2 other floats work in the area I usually cover, since they were short staffed that day!
I took 2 days sick, plan to talk w my manager Monday, any advice is appreciated.TY!

Sorry, not much space in the initial question for extra details: I started full time in the fall, thats why the 2 float days I am scheduled to work.
Legally, I can float all over the place,as was agreed when I accepted this full time position but morally I think if there is a space in my dept I should be there covering the same area I work the rest of the week,rather than sending me to work somewhere else and have 2 other floats cover my service. It makes perfect sense to me to be sent to the area I usually work if there is a need there.
I dont question the float part, as it was the initial agreement for the 2 days, but I question if I have a case to discuss with the manager and how the discussion could go. Of course I will keep it light and friendly, but I like to send a message"that's only so much someone can take if she is pushed around too much".
BTW, I know what a manager does, so please minimize comments that "I can be sent anywhere they need me" type. Thank you

It seems that you have a new schedule and that you're supposed to "float" (rotate the area in which you service). Apparently, all employees "float" based upon your question.

This could be so that everyone learns each other's job, which is both good (to learn other jobs) and bad (because then they can let people go, knowing that others are already trained for the job).

You can ask her again whether there is any issue.

You might be taking this the wrong way. Have you ever thought that the company might be testing you for a promotion or a transfer to another level? As long as you didn't get a cut in pay, just do as you're told, don't keep track of other floaters, and stop trying to figure out whether employees like you or not.

Project an attitude of confidence & act like you're happy doing your job. If you don't, it could work against you.

Stop being a worrier. Just be the best that you can be, no matter what your position may be.

Complaining to the manager could be a mistake.

Calm down & good luck.

Start complaining....and l make a fuss...then get your resume up to date and start looking.

since you already stated that you agreed to float as needed, then really, they aren't doing anything morally wrong--you agreed to it. talk to your HR person at your company-that's what they are there for