No, it is not true that Kamala Harris was selected as the vice presidential nominee by a bottom-up process from the grassroots level. The selection of Kamala Harris as the vice presidential nominee for the 2020 United States presidential election was made by Joe Biden, the then-Democratic presidential nominee. There was no formal or informal vote taken among Democratic party members to select her as the nominee.
The decision was announced by Joe Biden on August 11, 2020. He chose Kamala Harris to be his running mate due to a variety of factors including her experience in politics and government, as well as her diverse background which includes being the first Black woman and first Asian American woman to be nominated for national office by a major party.
The process by which the vice presidential nominee is chosen is typically determined by the presidential nominee. The presidential nominee consults with their team, considers various factors such as demographics, policy positions, and political experience, and ultimately makes the decision. This was the case when Joe Biden selected Kamala Harris to be his running mate in the 2020 election.
Therefore, it is not accurate to say that Kamala Harris was selected from the grassroots level or by a bottom-up process.