There is a rumor that the manager won’t give raises because her bonus will be smaller, anyone heard of anything like this?

Eve is writing the truth here.  It does not happen in ALL industries ....but in sales or production related industries  the team lead controls the raises and bonuses because they are taken from that person's profits

This is possible but it depends on how the bonus is calculated. Are non-managerial employees eligible for bonus?. If yes? how the quantitative part is calculated?

Why would anyone in her right mind listen to a rumor? 

Happened to me at a place I worked for 7 years. His bonus was based on the net profit of the plant.  Not only were they stingy with raises, but little perks started to disappear.  Took the free coffee away and replaced it with a vending machine (the place ran 24/7).  Took away the plastic silverware in the breakroom, citing "going green" and then took away the recycling bins! Used to cater a meal during peak times when people were working 12 - 16 hrs a day. Went from a nice meal to pizza to nothing. Used to offer gas gift cards now and then during peak to encourage some workers to work a longer shift.  The original manager appreciated his staff and the effort they went to to make the goals that had been set by the client. He stayed and worked right with them.  It all went downhill when he was replaced by another guy who didn't seem to do anything but talk sports with the male supervisors (females were shut out). Came 5 PM he was outta there no matter what was going on.  Same demands on staff but no support. When new hires coming in were making 50 cents an hour less than me I knew it was time to leave.