Is my horse being a brat or could there be something wrong?

So yesterday I went to were we board my horse and I got her out, brushed her, put her boots on as usuall. Then I took her in the arean and lunged her and she seemed okay. Then when I tried to lunge her on her other side she wouldnt lunge, and she kept trying to buck if I would try to make her go. So I fought with her awhile made her go around a few times then took her and saddled her. She didnt mind when I put the saddle on or tightened the cinch. Then when I went to get on she laid her ears back and turned her head around(she has never done this before) I got on thinking she is just being a brat and its just one of her tricks to make me not ride her. Then after I got on we walked around a bit I made her trot and she kept making like grunting sounds and she would kind of kick her legs and stop troting and then I would try to make her trot again and she would stop and fight with me and back up and stop her feet. So I walked around a few times and then got off and when I went to get back on she really laid her ears back and turn around as to if she was going to bite me (never done this before either) So I took the saddle off seeing if there was anything pinching her or poking her but I couldnt find anything. Then I pushed on her belly by her flank and she turned around and laid her ears back. If I raised my leg up like I was going to get one she would do the same thing to. She seemed to have a lot of gas but she was pooping a lot. I asked the lady there and she said she thinks she may just be being a brat. When I parents came they looked at her they said she seemed fine but she seemed to be acting a little strange. So do you think she is being a brat or maybe her stomach is bothering her.

I would say something was bothering her if this is not typically behavior. Or maybe in heat.

Maybe she ate something that has made her bloated. It could be awfully uncomfortable to trot and have a cinch tighten if her stomach was painfully expanded. If that's the case she should be fine in a matter of days at the most. If she still acts like that id have her vet checked. I wouldnt worry about it honestly. Humans have sick days, sometimes horses do too =)

Thanks for your thoughts :)

My advice would be get a chiropractor out to look at her. It sounds like she is probably stiff on the side you were lunging her. Were you trotting in the same direction that you were lunging her?