Very unlucky not getting event girls.

The flaw is in the design, using a static chance of getting the girl on each try. If unlucky you'll never get the girl. A possible solution would be increasing the chance a bit with every fail, starting at maybe 1% and increasing it with 0,1% with each fail, resetting to 1% when you get a girl. A cap on the chance would make sense, maybe 10% for the regular gilrs, and up to 50% for event girl. This way it will become somewhat easier to get the girls, while it still takes effort to get them.