I don't think that it's wrong to insist that this not be "at random," and that the policy be clear... "I have some concerns; can we talk?"
This is one of your DD's courses through a college/uni? A dual enrollment while also in high school?
I believe the preponderance of thought would be that:
1) DD needs to advocate for herself.
2) Parents are out.
3)
Insisting may be out as college is not a right but a privilege (different than free appropriate public education K5-12).
You might wish to coach her, helping her collect her thoughts and the pertinent facts, while explaining to her about advocating on basis of principle, where ALL may benefit... avoid having this be about her personal stuff: grades, stress, age, etc.
She may wish to review the syllabus, course schedule, etc, to gather facts while learning from you what best policy/practice looks like. If there is no mention of due-dates rather than end of semester, and no mention of late policy, she may wish to ask about these things. She may wish to use the same style of presenting her confusion and asking for the teacher's help, which you've recently shared for working with elementary schools, thereby learning what the due dates and policies are. Her bottom line may be advocating for proactive written notice of due dates and late policies.
If, on the other hand, the college has due dates but her high school has only end-of-semester due-dates, then this is merely different than what she is used to. As it is a college course, the college rules may supersede the HS rules she is familiar with.
Schools may be taking note of her ability to self-advocate and hold her own, while remaining respectful and building rapport with her professors, as these will be important life skills she may be undertaking on a college campus soon. In handling both her disappointment, her willingness to perform on schedule, and this advocacy opportunity, she may be influencing decision makers about ALL early college entrants. She may wish to be gracious, thanking the professor for his/her time. Above all, she may want to demonstrate that she takes personal responsibility for her education, her time management, and her choices, including tone of communication. (This is an initial disappointment, this is not dealing with an entrenched problem, where parties may be fully escalated.)
Do not play the age card; do not ask for any special privileges or leeway. If someone else puts that subject on the table, quickly side-step it to re-focus on the subject(s) at hand: due-dates, late policies, and managing expectations by providing proactive notice of these things (on a syllabus, for example).
Just my 2 cents.
