Warren definitely isn't "to the left" of Obama on foreign policy (assuming "left" vs. "right" on foreign policy is isolationist vs. interventionist). For example, she often criticized the Obama administration for not being pro-Israel enough and was probably the biggest Israel booster in the Democratic Senate caucus after Schumer. She definitely doesn't prioritize foreign affairs the way some Democrats do (it's not her area of expertise), but she is undoubtedly a hawk within the bounds of the Democratic field and quite far from Sanders on the topic.
Huh? What are you talking about here? Warren was one of only 8 Senators to boycott Netanyahu's speech before Congress in 2015. Unlike quite a few Democratic Senators (including other 2020 hopefuls like Booker and Gillibrand) she did not attack the UN for its anti-Israeli settlement resolution last year. And for that matter, Rubio's resolution attacking the UN for said resolution has 78 co-sponsors, including Booker, Gillibrand, Harris, and Klobuchar, but *not* including Sanders and Warren:
https://www.congress.gov/bill/115th-congress/senate-resolution/6/cosponsorsThere was also this letter from a few years ago threatening the Palestinian Authority over its participation in the ICC, signed by 75 Senators (including Booker, Gillibrand, and Klobuchar), but not signed by Warren:
https://www.dailykos.com/stories/2015/1/30/1361281/-75-Senators-Sign-Letter-to-Kerry-Defending-Israeli-War-Crimes-Demanding-More-Palestinian-SufferingSo I am unclear on what makes Warren more hawkish on Israel than Obama, or what makes her "probably the biggest Israel booster in the Democratic Senate caucus after Schumer". How in the world does one reach that conclusion? She seems to be about the same on Israel as Obama is, and, as I mentioned in my earlier comment, she's to his left on some other foreign policy issues, like arming the Saudis and Syrian rebels. I see no plausible rationale for saying that she's one of the more hawkish entrants in the 2020 Democratic field.