What are the danger signs of internal bleeding?

Wife had laparoscopic cholecystectomy yesterday and overnight the blood pressure is dropping. Was 100/65 after op. Currently 90/51

Her normal blood pressure is a little on the low side (110/75)

She has numbness in fingers and toes. But pain in heel

She has just been to the toilet and passed about 300ml of urine (it has been about 18 hours since surgery)

She has had at least 2 litres of sodium chloride via IV drip (125ml/hour)

Pulse has been on high side overnight 98-100 but doctor says now normal

She is currently on a Potassium drip and has been told to drink plenty of water.

EDIT: Temperature normal

Doctors said will monitor for few more hours but will probably send her home today.

We are concerned about possible internal bleeding. What symptons should we look out for?

Relative died from complications 4 days after same surgery 9 years ago!

Are there any questions we should be asking medical staff? Any advice / suggestions? Any tests we should ask for?