I am not talking about his supporters here on DU but those in the general public. Those issues are:
Health care
Income inequality
Climate change (albeit to a lesser degree)
Bernie is driving the left flank on all of those issues. The moderates (Biden, Bloomberg, Buttigieg, Klobuchar and somewhat Steyer) are not as strongly left on those issues as Bernie. As such, the energized rank and file may not see other ordinary citizen Dems as being committed to their issues.
I am not saying one side is correct and the other is not. I am simply offering my explanation for what I see happening.
As an example, I followed a Twitch streamer for the past couple of years. Hes a good, liberal guy in his 20s. He is definitely not a MAGAt. A few months ago, he expressed (on Twitter) his strong support for Sanders and his platform. He is all in for Bernie for his health care and income inequality stances. He refers to other Dems as corporatists but seldom goes too negative on them. Still, it is health care and income inequality which he mentions frequently. What issues do the other Dems (besides Sanders and Warren) seldom touch upon? Health care and income inequality. Expanding the ACA is not a viable solution for a lot of people given the gig economy we have now which makes employer based health care a dicey one for people.
So it is possible that your friend may not think you are committed as much as she is. I am not saying your friend is correct here. Im simply saying that is probably how she feels.