It's become almost impossible to get 1 much less 2 girls during event revival events.
I haven't missed a single event girl in about a year. Although I've only got one from this event so far so it could still happen.

You also get enough kobans to do a spin every month or so, although I've never got an event girl out of it I think (only generic ones) so it probably wouldn't help.

Tbh I don't get where they're going with the monetization. $40 to get one random girl is outrageous compared to any other game out there, and that's pretty much the only thing you can spend on outside of refills (which are pretty worthless with the rate they're releasing content at). The monthly card is finally a step in the right direction, but it only gives 1/3rd of a spin after a month so it's pretty much negligible.