The grandma has a hidden meter that starts at 65 (to get the first encounter happen faster, but could have increased it further as you said :D) and when it gets to 100 she will appear. Breaking ice increases the meter by 17 and the meter ticks down by 1 every second. I spent almost all of the last day balancing and it was 100% the hardest part of the project and could have done a waaay better job at it. Thanks for the feedback!