Snopes has an article on this that mentions amongst other things
Harris was speaking at a roundtable with disability advocates, who
were discussing the impact of the Supreme Court's reversal of its 1973
Roe v. Wade decision concerning abortion rights on people with
disabilities (...)
(which happened in 2022) and points out that
self-description was consistent with both a commitment to gender
inclusivity and best practices for accommodating people who are
visually impaired.
So this is on brand for her as a matter of (presumably) personal values as well as political strategy to accomodate people with disabilities or their representatives.
The video for the event is here: Vice President Harris Meets with Disability Rights Leaders. Several (but not all) people introduce themselves, or are introduced, with gender pronouns, and/or references to ethnicity or appearance.
Given that all people attending seem to read prepared statements I assume this was intended to be filmed and broadcast, not as an actual discussion, which might make the way of introduction part of a public/political statement.
Here is the transcript of Vice President Harris's remarks: Remarks by Vice President Harris in a Roundtable with Disability Advocates.