MrWebster reminded me that the Podesta emails mentioned Senator Warren several times.
This gives us a window into Warren's "private" positions.

Warren provided Clinton list of staff picks

U.S. Sen. Elizabeth Warren, D-Massachusetts, reportedly provided Democratic presidential nominee Hillary Clinton's campaign with a list of potential administration staff picks, according to allegedly hacked emails published by WikiLeaks Tuesday.
The alleged email, which reportedly came from Clinton Campaign Chairman John Podesta's inbox, highlighted the Massachusetts Democrat's skepticism and her efforts to keep individuals with Wall Street ties out of the possible next presidential administration, Politico reported.
...Release of the alleged exchange came one day after WikiLeaks reportedly published a slew of emails, including one in which Clinton's campaign raised concerns about upsetting the Massachusetts senator over banking proposals.

Politico reported last month that Warren had developed what some called a "hell no" list of possible appointments she would oppose in a Clinton administration, including those with ties to big banks.

This is good news and bad news.
The good news is that Warren is serious about reforming Wall Street in private.
The bad news is that Warren was BFF's with the Clinton campaign.

Hollywood Friends

A top aide to Hillary Clinton was incensed by MoveOn.org’s campaign to draft Sen. Elizabeth Warren (D-Mass.) into the presidential race.

“This is more than a little annoying. Making noise is one thing. Spending seven figures is another. She voted for the war, you punished her already, get over it,” Reines’ email reads. “I don’t know who funds them, but don’t we have Hollywood friends with ties to MoveOn who can tell them to cool it?”
There is no evidence that the Clinton campaign took Reines’ advice.

Early on

The emails show in great detail just how aggressively and comprehensively the Hillary Clinton team pursued Elizabeth Warren for support, beginning as early as the spring of 2014 – a full year before Sanders had even declared his candidacy.
...
On the same date, November 18, 2014, and in the same thread, Abedin indicates that whenever Warren says something publicly that is “critical” to Hillary Clinton, members of the Clinton team are to call Warren down on it. Abedin also indicates that there have been ongoing discussions with “Mindy,” (Mindy Myers), Warren’s Chief of Staff at the time and implicates “Mandy” (Mandy Grunwald) as having “been helpful.” Mandy Grunwald was a top strategist for Senator Warren at that time, but according to Abedin, was providing “good intel” to the Clinton team. The leaked emails back that up. Grunwald had been an advisor to Bill and Hillary Clinton for more than two decades but it was not officially announced that Grunwald was joining the Hillary Clinton campaign until February 2015.

“There is some background here that Im happy to share. Mandy has been helpful and will provide good intel. As for Mindy, we have frustrated her but yes she will also be very helpful. But I think everytime EW [Elizabeth Warren] says something interpreted as not being effusive enough or critical, she hears from a Neera, Gillibrand, Mandy or we suggest that Dan talk to her policy person. Basically her people are saying say enough already, lets just talk direct. We should assume meeting will leak as we are currently doing it at a hotel in Boston and I am sure they are prepared for that too. We conveyed that we are happy to meet wherever EW wants.”