Special Counsel Robert Mueller is expanding his investigation into Trump campaign collusion with Russia by looking at a brief encounter between the president's daughter Ivanka, and Russians who attended the Trump Tower meeting with Donald Trump, Jr. in June, 2016.

Ivanka apparently met the Russians outside of an elevator in Trump Tower and "exchanged greetings." Naturally, this makes her a suspect in Mueller's world.

Los Angeles Times:

Investigators also are exploring the involvement of the president’s daughter, Ivanka Trump, who did not attend the half-hour sit-down on June 9, 2016, but briefly spoke with two of the participants, a Russian lawyer and a Russian-born Washington lobbyist. Details of the encounter were not previously known.

It occurred at the Trump Tower elevator as the Russian lawyer, Natalia Veselnitskaya, and the lobbyist, Rinat Akhmetshin, were leaving the building and consisted of pleasantries, a person familiar with the episode said. But Mueller’s investigators want to know every contact the two visitors had with Trump’s family members and inner circle.

Mueller long has sought to nail down details of the unusual gathering at the height of the presidential race between three of Trump’s top campaign aides — his eldest son, Donald Trump Jr., his son-in-law, Jared Kushner, and his campaign manager, Paul Manafort — and Veselnitskaya, Akhmetshin, plus a Russian language translator, a U.S.-based employee of a Russian real estate group, and a British music promoter with Russian business ties who helped bring the group together.

Ivanka Trump was unaware of the subject matter of the meeting. She wasn't present. Why does Mueller want to investigate when all she did was politely say hello and exchange a few words with some Russians?

This is not a question of Mueller being thorough. He is trying to ratchet up the pressure on the president and his people. 

There's also this curious tidbit from the Times article:

Some defense lawyers involved in the case view Mueller’s latest push as a sign that investigators are focusing on possible obstruction of justice by Trump and several of his closest advisors for their statements about the politically sensitive meeting, rather than for collusion with the Russians.

If Mueller has dropped the collusion probe, what's he still doing with a job? There's no way to prove that Trump knew the subject matter of the meeting. Mueller is fishing and desperate to find something criminal on Trump to satisfy his real clients; Democrats who are angry they lost an election and wish to overturn the result.