How long ago was her c-sec? Is she getting and abortion or is this a required d&c?

She had the c section only two weeks ago. The d&c is required to clean out some clotting and possibly left over placenta.

I heard it's rare to require a d&c after a c section

I'm assuming she is still bleeding quite a bit and having a hard time because tissue is left inside her, and that is why they want to do the d&c, right?

What are her options? If she doesn't have the d&c, is she at risk of infection? In which case, wouldn't that cause more scar tissue?

These are questions you should ask the doctor. Perhaps a second opinion.

She went to her ob for a post checkup.

She is still bleeding and then ob suspects left over tissue.

The ob performed the cs and the checkup. She will also be performing the d&c.

The ob has advised that leaving the tissue in will most likely have worse repercusions than having the d&c due to the risk of infection.

I've asked her if the ob mentioned any further details but she doesn't think so (understandably she has a memory like a goldfish at the moment)

A d&c is a fairly routine, straight forward procedure. There is risk with any operation and you'd need to weigh those risks with the eventual outcome.

Good luck.