I've saw this game before on youtube.
Nice art you have.
About the freeze you should add FPS text on the top of the layers, so you can know exactly where the fps drop.
Add text to top non parallax layer.
And add this event :
Every tic --------- Set text to : fps & " FPS (" & renderer & ") " & round(cpuutilisation * 100) & "% CPU "
Now make all your characters animation speed to 0, except the girl, and test your game.
I'm sure 100 % the fps drop is from the characters animation frames.