Fusion is possible, but you need 100s sex appeal divines in your category of girls (hoes OR actresses). 

98/100 SA girls are not eligible.

For fusing a 100 girl you need a second 100 of her ethnic plus two more 80 somthing (here you can downgrade a potential 90s girl in the gym).

Furthermore you need 2 more 100 of another ethnic and 1 of a third ethnic.

Then you got check your target girl and add the formerly mentioned other girls. When you got all green portraits you can fuse here.

But be aware during this process you will lose all of the formerly mentioned girls for good.

The fusioned/target girl is ready for genetical upgrades (but further fusion needed when you reach 120 SA) with hormones ;-)