I had a fairly annoying experience with the update. I was grinding level 9, was getting ready for the last stretch, already spending 110 Sp on updating Anika and Delilah just to have them demoted to tier 3&4 respectively overnight. Their income dropped from 11 Sp / s to around 10 Qa / s....that's a 99.9999% of my income.

So far it seems to me girl no 06 will be important. The higher tier girls all have an 50 level jump to next tier, to go above the 1e21 income range. But the tier 06 girl only has a 25 level jump in that zone, which makes her the best earning girl. (1/10th the cost to reach the 10-20Sp / s income compared to all others)

Of course all this applies to the new players as advanced players will just zoom past this with high multipliers.