Honda accord keeps getting hot?

My 2004 honda accord ex 2.4 keeps getting hot, after around 5 minutes or less when I first start it it starts going up and then like 10 minutes later its all the way on the red line we replaced the thermostat what else could it be? My sister drove it around 140 miles with it on hot almost to the red line could she have messed up the engine? Is there anyway to check it if its worth fixing or getting a new engine?

Is there excessive white smoke coming from the exhaust when you startup? If so, that could be a symptom of a blown head gasket which is very expensive (better look for a new car). Or it could be as simple as the coolant level in the radiator is low (open when cold and with care).

You haven't exhausted your search for the problem sufficient to consider a new engine an option. For instance, the replaced thermostat may have also failed. The radiator cap may be failing. It may need to be flushed and have a pressure test administered to see about leaky hoses or fittings. Keep the reservoir for coolant filled up to the "full" line when the engine is cold until you have the time to get your mechanic to further troubleshoot the over-heating problem.

Flush the cooling system. Get the cooling system pressure tested. Bleed the cooling system. Check if the fans are running. Check for a bad water pump. Check for a clogged radiator. Check for a blown head gasket.

Your screwed likely vlown the head gasket and thereccould be other damage as well.

Since you are guessing and throwing parts at it your engine will suffer death if you are wrong. Check that the engine fans are working. They should come on when the AC is turned on. Buy a infra red temp checker and locate where the blockage of coolant is. And if the temps are what the gauge says. If you changed the T-stat is it installed the correct way? If this info is over your head take it in to a garage.

Driving a car with an overheating motor is a sure way to blow out the head gasket and i this case the cylinder head may even have warped!
If you haven't been doing oil changes every 3,000 miles and have high miles on the motor a different motor may be best.

It is not an engine problem,
1) The water pump is bad which will cost you a few hundred
2) The Radiator is clogged. Your radiator fluid will look reddish brown
3) The new thermostat is no good. This happens often.

If you run it hot too long and the coolant runs too low then you can cause permanent damage. We used to drain cars of coolant that we ran in Demolition Derbies (so hot coolant was not spraying all over the place) and hope they lasted long enough to outlast everyone else. About 15 minutes like that killed the engine.

Have you checked to see if it is really hot or is the temperature sending unit bad.

Do you have coolant in the system, or rusty water? A rusty mess will clog the radiator.
Do you have a cap that will hold pressure? Necessary for proper cooling.
Do your fans work? Needed for cooling.
Is your radiator and AC condenser clogged with dirt, leaves, or bugs?
Have you had it checked for a bad head gasket?

You have no idea what a thermostat does, so you blame it.
FIGURES. EHH WRONG!
Most likely your coolant level is LOW. Check on a cold engine. It is safe to check at this time. One that has been parked overnight. Then before you start the engine you pop the hood and check all the reservoirs. And see where the coolant level stand at. If it is below the minimum line then move it up to the proper level by adding coolant like 50/50 mixture. Make sure there's nothing blocking the airflow into the engine through the radiator such as a car nose bra.
If all the driving was in bumper to bumper traffic, the rad fan should be kicking on when the temperature is up high. If you do not hear the fan going when the temperature is near the red line, then you blew a fan fuse(most likely) or something else electrical is wrong with the fan. A relay perhaps? Have a mechanic check it out. There's very little else it can be. So long as you did not open the rad cap while it was hot and add cold water to it(anything less than boiling hot is COLD) then no damage is done YET. No head gasket problems, nothing.
A mechanic can fix it so it is working right. Not an engine job, not YET AT LEAST.

40+ yr mechanic