From the forest, go right. Keep going right until you see an area by a lake. Run along the coast until you can walk on the ice. Pick up the Potion and go northwest. You’ll come to an area with lots of little icebergs. You need to cross them so pick the top option. The icebergs will change when you jump on one surrounding it. If they are raised they will submerge, if they are submerged they will raise. If you surrounded by submerged icebergs you will sink and have to start again. To get across you need to make sure going to jump on one that is surrounded by raised icebergs because if you do they will submerge when you jump and you will sink.
When you make it to the other side go north into the cave. Pick up the Safety Bit inside and go back past the icebergs and head to the exit in the right corner, pressing Select might help. Go right at the tree and keep heading north east. At the next area, there is a path to the top left, bottom left (where you should be), one to the bottom right and one to the top right. Take the path to the top right. Go to the top left and on the second screen of this there should be a blue Added Cut materia on the path, it’s kinda hard to see. When you have it go to the top left again. On the next screen, with some steaming lakes, run towards the water to the left. When an option appears choose the top option. Keep going to the north west. Then go left. You’ll be on a vast snowfield. You should place markers with O to plot your course. Go north and mark your course. The wind can blow you around, so use the markers to make sure you are always going in a straight line north. You should come to a cave. There is an All materia in the tent. Get it and return to the snowfield. Keep going north to arrive at a shack. Enter it and talk to the man here to rest and save. Leave the shack and your friends will be outside. Talk to them and head south back to the snowfield. Go south until you get to the cave. Don’t enter but now go east. Keep going east until you get to a new area. Head south and east to get to a cave. Cure yourself, and talk to the person here. You’ll fight a boss…
Basically stick to Fire attacks, as Ice will heal her. Bahamut and Ifrit should do it. She attacks with Cold Breath, Ice2 and Fascination that confuses whoever it hits.
After the battle, you can pick up the Summon Alexander materia left behind. Now return to the shack to rest and save.