The main key for this mission is to utilize Colin's cheap units to quickly capture the airport and the base in the center of the map to spam units, namely, B copters.
First, build three infantry, and Lash will respond in turn. Now with your two left-most infantry, move the top one to the top of the screen into the woods as far it can go. For the lower one, move it along the road towards the bridge. For your last infantry, move it towards the airport at the bottom part of your side of the map. Build an APC and an infantry - make sure the infantry can get into the APC - and build the APC on one of the leftmost bases, it doesn't matter which.
After Lash has done her thing, load the infantry into the APC and send it as far as it can go left - don't drop yet. For your top left infantry move it across the river, ready to capture one of those cities. For your bottom left, move it onto the city - but do not capture - you're moving to the base next turn. Move your right infantry towards the airport again, and get ready to capture that. Don't build and end your turn.
Now capture! Move that APC and drop the guy on the airport, capture a city, that center base, and that airport on the right. Build a tank.
Once you finish capturing all those, start throwing B copters and tanks at Lash. Try to fly over a T copter with an infantry unit to capture her airport - and continue pounding away with B copters and cheap tanks (they can be Medium tanks too) and you should not have any trouble whatsoever.