I'm not sure about this but if I remember correctly so I've seen a scenario where Eva will appear in the party even she lives in with Vivian or it was just a bug.
Edit: I can confirm this, Eva can be invited to a party with Des even though she lives with Vivian.
This is for sure, Eva doesn’t need to live with Vivian that she can be invited to a party.
(you invited her in campus)
The way to get Eva invited to the party is to avoid Harper’s blackmailing route and you help Eva.
Edit:
Sorry, you must send her the paper and then you have to be Dom route(Tell M.S Harper fuck off) or your Bluffing must work with M.S Harper(You need at least three lie points)
Edit: Sorry, that was how to you invited her live with Vivian
Edit3:
You must send her the paper, then you can invited Eva in the party at campus.
Edit4: Nevermind.... As far I know " Try and help her write it in instead " choises you cant invited Eva in the party I guess you meant by "help" that?