Social media can be a toxic environment. People can argue their case vehemently. If people feel their reality and experience is being infringed they can accuse their opponent of gaslighting. I worry about the extension of this use of the word.
Reality is socially constructed, but not totally socially constructed. Reality is constituted through active shifting of moving and multiple points of view reinforced by social perspective-taking (see eg. post on my Relational Psychiatry blog). The models of the world we create do not necessarily describe the real world (see eg. another post on my Relational Psychiatry blog). Just because people disagree and feel their reality is being questioned, does not mean they are right or gaslighted. Since the Enlightenment at least we have had to debate the nature of truth.