Hello, SoulSail.

The woman seems to be a guide or helper as you said - the role of co-worker (somebody who works with you) seems to suggest that as well. The erotic undertones often happen because of the potential of higher body merges, often misinterpreted as offers to sexual contact by dreamers. This can also be present in kisses, touching, hugs and embraces.

The school would indicate a higher plane like the astral or mental, whereas the campus is the wider plane itself.

Her presence in three different nights seems to suggest an inner sense has come online or is being trained - the one where you pick up the same ident and recognise the person associated with it. So, you're to remember and recognise this entity when it appears again.

Older/younger as well as taller/smaller often help identifying differences in quality or development of persons or entities. Another inner sense impression rendered into a visual image.

The impression of being late to class may mean that you feel you have to catch up in one aspect of your life (here the nonphysical one) with the developments that have happened elsewhere (the physical one, what you did instead of "studying"). Math is often used to represent more advanced topics, as most people consider math to be hard.