2003 Ford Focus A/C shuts down car

I have a 2003 Ford Focus- When I bought it the dealer(used) told me there was a compressor problem but when I took it to a mechanic he said it was some sort of electrical problem that would take "in depth" assessing.

No check engine light. New alternator.
It sputter the moment the AC goes on, and when I stop it shuts down completely. I thought I could handle not having ac but the heat is getting worse. Help please! I would love to fix this myself if possible!

It is possible and I don't mean to offend but the girly avatar make me wonder.
Two things come to mind. One is the throttle body and air by pass vale need cleaning. Common problem for Fords stalling at idle. Google is your friend on this one. The other is that the A/C system is over charged. Common problem with idiots who think A/C pro is all they need to fix A/C problems. This will take a can of A/C pro that has a gauge on the line. Don't open the can we only need the gauge and it is the cheapest thing available. Hook up the hose with the car running and the A/C on. The pressure reading should be in the green, 40 lbs no more. If it is higher then your killing the compressor and stalling the car let it out.

Electrical. You don't want to mess with it innless its just a loose connector which I doubt