No inspection, 20 year old house, slab has 5+ inches of pitch

[Justin Kurpius]

I’m hoping this community can help.  My mother bought a house in a large well known retirement community in Northern Illinois.  Most all of the 5000+ homes in the community were built in or around 1999.  The house seemed to be in good shape during the walkthrough. Her cash offer was accepted.  She moved in two weeks later.  The house is a 2 bed, 2 bath ranch sitting on a slab. 

A few days after moving in, she noticed a slope in the floor.  After measuring, we concluded a roughly 5 inch pitch from the north end of house to the south end.  We also noticed a rather large “valley” in the roof....basically and area that looks caved in.  The roof was recently replaced.  

The house had two offers accepted and then backed out of before my mom bought it (which she did not know).  She did not order an inspection.  Her reasoning was because the house was not old and she did a walk through concluding it was a good house with no visible problems. She has lived in the house for about two weeks now. 

My question:  Can she do anything about this even though she did not have an inspection?  The seller did not disclose anything on both matters.   Ideally she would like to back out because It was not disclosed.

Thanks!

Justin