I think what she means is User1 doesn’t want User2 to see their posts. If User1 ignores User2 that will just prevent User1 from seeing User2’s posts, but User2 will still be able to see User1’s posts - and that’s what they are trying to avoid.
If an admin were to go into User2’s preferences and manually add User1 to their list of Ignored Users, that would work… but it could also open up a Pandora’s Box should User2 realize what was done to their preferences.