If she is having accidents into her pants, this is called "encopresis".  Children often have developed this problem after an earlier problem with constipation -- as a 2-3 year old, they will have a painful bowel movement, then become fearful that the next one will hurt again, so they hold onto the next one until it becomes large and hard -- which hurts even more and sets up a cycle of withholding behavior.  Eventually stool will leak around this lump of hard retained material, and leak into the pants.  Treatment involves keeping the bowel movements soft, sometimes with mineral oil or other stool softeners, for a long period of time, often at least 6-12 months, so the child forgets that having a bowel movement is painful.

See attached link to handout.

What I did was, make her sit on the toilet, bored, after each time, since she didn't want to stop playing to go. Once she discovered that she was losing playing time by not stopping to go, that was over.

Who is cleaning up the messes?  If this isn't about a physical inability or illness, if this is just a behavior, one way to help stop it is to make your child responsible for her own behavior.  When she soils herself, very matter of factly explain that it is her poop, and her responsibility to help clean it up.  Don't fuss or yell, this is all about being straight forward, and letting her decide when she's ready to solve the problem.  She needs to take off the soiled clothes and dump the poop into the toilet, and put the clothes where ever you designate.  She needs to sit on the toilet and wipe as well as she can with tp, or clean up with baby wipes, a shower, whatever it takes.  Your job is to assist and to remain calm.  Once your child understands that she has to handle the soiled clothes, and clean herself up, and that pooping in the toilet makes that unpleasant job much easier, she will probably make better bathroom choices.

Good luck, and stay calm.  This too shall pass!