First to be sure I picked the 'looking for romance' in the beginning. I also always choose Viv to be dominant.
I didn't help Eve. I don't want to have to deal with Ms Harper because of Eve.

I think you have to be nice to her and support her. But the important part is to not to let her sleep over! Even Tara mentioned it at the salon.
However do invite her to the party.
Yes, you have to 'sell the kiss' when Viv meets Des when they go shopping to have a romantic relationship with Des. The middle option probably does nothing and the last one is for the dominant route.
Might probably ask about Tara about Des to tell the game that Viv is really interested in her. But the important parts are the kiss and the sleep over.
At the party to avoid trouble first choose to dance with Des. Viv can dance as close to Des as you want. Then go to the bar. Becca greets them there and Malina tries to be annoying. Reject Becca and stay with Des. Enjoy a couple of drinks with Des and at the end definitely go with her. You wouldn't want to miss a scene with her, right?

After the party when Viv goes to meet Des at the art studio it doesn't matter if you accept Eve's invitation to the sorority party as it's incomplete anyway.
Feel free to have Viv be a model for Des, you won't see the result on the romance route anyway. Mind you, Des paints Viv differently depending on the kind of relationship they have. Enjoy another hot scene at the dorm.
Few days pass and Des doesn't call or message Viv so she decides to pay her a visit. If you've done things right, the final choice for Viv is to confess her feelings to Des. Des will finally be serious for a long enough time to listen to Viv and not dismiss her outright.

The end.
Well not really, but you have reached Desiree's best ending.

If you accepted Eve's invitation, go see the party. There are a couple of hot scenes. I recommend looking for the girl with the white crop top and black hair. Her scene is quite hot. Viv can have fun with Ms Harper too, but her scene isn't as hot.
No matter what you do, probably the last scene is Viv going to a date with Ms Harper. I didn't bother with it, so I can't say for certain. I think it's because the game wasn't finished and the last part is bugged. Even if the original edition was left unfinished, we at least got a good ending with Des.