pa96xj

Friend of mine has an 07 (I think) grand Cherokee and sometimes when she puts it in drive it just revs up. The little box that tells you your in park, reverse, neutral or drive is showing up in all gears. When you shift from park to drive the little box is lit up in all gears ( park reverse neutral and drive) and when she gives it gas it just revs. Only does it sometimes. She will go to a stop sign and when she goes to pull out it will just rev and all the boxes are lit up. Any ideas? Neutral safety switch? Low trans fluid? Thanks guys let me know what yas think.