@mecabag I think what people are objecting to is not so much the "gender reveal party" (although how she managed to have one during lockdown is indeed a mystery) but more the fact that she (1) verbally abused the sonographer (2) is using emotive language such as "devastated" and "ruined" to describe her feelings about the sonographer accidentally telling her what kind of genitals her healthy baby is, when many of us have been devastated to learn that our baby has no heartbeat or has a serious health condition, and (3) has taken her "story" to the papers despite having been refunded her money and given an apology present by the scan company.
The tackiness of a "gender reveal party" is neither here nor there. If she had posted a thread on AIBU about nobody wanting to come to her gender reveal party and everyone had laid into her then you would have a point. But that's not what happened. People are commenting on her behaviour and the fact that she comes across as an entitled, stupid little gobshite.