MOSCOW — When American prosecutors accused a senior Russian official’s son of laundering $14 million by investing in Manhattan property and other assets, she was called to defend him. When Moscow regional officials battled Ikea over the Swedish retailer’s expansion, she took on their case.

Natalia Veselnitskaya, the Russian lawyer who met with Donald Trump Jr. last year to discuss possible compromising material on the Democrats, has been widely depicted as a one-issue activist consumed with getting Congress to repeal sanctions against Russian businessmen.

But lawyers and others in Moscow’s legal community called her a trusted insider, one who could be counted on to argue and win important high-profile court cases that matter to the government and to one senior, well-connected official in particular.

Ms. Veselnitskaya, 42, earned her status as the go-to lawyer for the Moscow regional government. For years, she has been a lawyer for the Katsyv family, whose patriarch, Pyotr D. Katsyv, was minister of transportation of the Moscow region for more than a decade, and whose son was caught up in the New York money laundering case.