Quickest way I can think of helping you is to replace two of your pokemon with a walrein and bronzong (bronzong needs to have levitate, doesn't matter for walrein).
Keep both alakazam and scrafty, everything else is useless against Terra due to her field effect. buy an air balloon for scrafty (this will help when it takes on her excadril). Alakazam is needed to get past nidoking, but don't bother setting up with it.
Ideally, you want terra to get to a point where she sends out her claydol. At this point bronzong needs to come in and set up trick room (which you have the tm for and need to teach it). Then send out walrein and kill everything with blizzard.
Alternatively, if you have a drapion and a few tanky mons/mons with protect in your PC, when the claydol comes out, send out drapion with air balloon and set up 2 layers of toxic spikes. You can then proceed to use pokemon and items to toxic stall out the rest of her team once nidoking and excadril are slain. Drapion with an air balloon works best to set up T-spikes as claydol cannot do anything to it other than explode. Generally it takes the AI several turns to realise this, as with the air balloon, drapion is immune to everything else claydol has.
Hope this helps.