I see what you mean Eddie but it's nothing specific to her regarding why they don't want to meet her - it's nothing she could explain or really overcome. They just know she's part Black and they're not here for it.
I kinda see why she didn't bother - their mind is made up already. Ton shared with us that his mom told him not to bring home a White girl - now if he chose to go out there and fall in love with Sarah he couldn't be too shocked or surprised when his mother didn't really accept the relationship. And there's probably very little Sarah would be able to do to overcome .
Her partner gave a fair warning that his parents are clearly not here for mixing the pot. She chose to go there anyway and test the waters. It didn't work out for her. She just has to move on and decide whether or not she can live with the fact that her husband's family doesn't accept her - this could prove to be a huge hurdle for their relationship, considering that they aren't married yet.