In addition to what Abi said, as for not being able to see objects and portals on your end. Make sure for your objects, you are creating new object groups when adding in custom meshes you've downloaded. By adding custom objects to default groups, you won't be able to see them.
As for your crashing friend, the above /could/ be making her crash. As could some custom weather files, if you did these, have her remove them.
For not being able to see portal, be sure to go back and check the portal coordinates and make sure you've got the option checked, then test in map maker to be sure it's there.