The most common cause is a dirty/malfunctioning vent system.

Undo the dryer from the exhaust
Run a load
If the load dries correctly then you have a vent problem.
Clean/check the vent system. Make sure the outside louvers open fully.

If you do not want lint in the house.
Take a pair of pantyhose, put one leg into the other and attach this to the dryer exhaust.
Leave enough room behind the dryer so it can blow out like a windsock.
Run a load.

Both the above will allow you to check the air flow and temp.
Also the above is NOT recommended for a gas dryer due to possible carbon monoxide problems

Here are your parts
Replacement parts for WHIRLPOOL GEW9250PL0 Electric Dryer | AppliancePartsPros.com

Here is the tech sheet
http://www.servicematters.com/docs/wiring/Tech%20Sheet%20-%208558722.pdf

And a manual. Not an exact match to your uinit but should be close
https://secured.whirlpool.com/Service/SrvTechAdm.nsf/2cd44500d572193285256a45004fd9d6/cdce3c10dcb5382285256aa20064beaa/$FILE/Duetdry.pdf

I am assuming you also checked the vent louvers to make sure they open fully.

I would run it disconnected from the vent.
This will let you monitor the heat and air flow on different settings..

If she is running the unit in an auto mode, it could be a problem with the moisture sensor.

If it does not have decent heat it could be the thermistor. Check it with a meter.

If you cannot regulate the heat it could be a grounded element.
Remove power from the unit. Remove both wires from the heating coil and measure it with a meter, Should be about 10 ohms. Then measure from each terminal to the frame, both should be infinite resistance (open).

Worst case scenario is that it is the control board.

If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.

There is a good STICKY at the start of this forum about it's use.