Do i forgive her?

my girlfriend about a month ago stayed after skool with me and a few other ppl to do a project. i left early because my parents had to go somewhere. she walked me to the car but went back to finish up with other people. All the group left and she was the only one in our grp left. Another person from a different group stayed. i found out that they were huggin to keep warm and she was walkin backwards. then she tripped. he picked her up and purposefully fell back the other way and grabbed her on to him. i heard that although she didnt kiss him or anything but she stayed on top of him for awhile. he asked her to kiss him and she said no but she didnt try to get off of him and stayed there for over a minute. do i break up with her or forgive her? fyi she is a little too flirty with other guys but never done anytin serious til this.