I had no major problems with this one fight (I had to load save once). Fighting does not require destroying the net in order to win.
The giant spider isn't terribly dangerous until she gets enrage. Until then, all the little spiders must be killed. When she gets enrage, the fight is a pretty big race against time.
If you don't kill her quickly enough, she will decimate your party. For this moment, save your strongest skills.
It's also a good idea to drink a potion of speed. With a bit of luck, she will die in one turn.
In my opinion it is a very nice fight, although not very difficult.
It is much more difficult to fight with a spectator
I always love these posts where people are like:
"I did this fight without losing on my first try, with no prior knowledge of the fight, didn't us the webs for fall damage, or any cheese like stealth-killing her eggs or the two other phase spiders roaming around her area first. It was easy, you just need to get gud" 
