Overheating light comes on for 1 to 2 mins goes off..

Yep generally it's a head gasket failing on the generation 3 etc etc many have been through this and many are going through it I just finished with this

 

head gasket

 

You don't state how many miles you have on it.
I would suspect the water pump. You can purchase just the impeller and replace that.
A lot less money.
And the engine has been overheating, which is not good. Hopefully, you don't have a warped head.
But it's likely the head gasket is failing.
You need to get to a good place that knows about the Prius...

 

Change the pump first. It is a good move even if the head gasket is history. Use only dealer supplied oem; counterfeits with Toyota packaging are all over ebay and amazon. Normally the hg causes random first start severe rattling weeks or months before it causes lost coolant.

Future fyi... The coolant light will never come on without an underlying issue, coolant loss is never normal and dealer mechanics occasionally give bad advice based on an individual's level of experience. Normal combustion gas or leakdown tests are not definitive hg tests on a gen3 engine. Pressurized coolant combined with a quality borescope can be diagnostic in the hands of an experienced tech.

There may be one Toyota Master Mechanic at a dealer and she might be working on my car, not yours. Service advisors often know less than the oil change guy and usually were never skilled mechanics.

 

What’s the miles on it, and what miles was the EGR cleaned? Intake manifold cleaned as well? Any chance of a stop-leak product in the coolant?