you don't find many time stop scrolls in the game so you might want to memorise it in case you don't find another. If you're having too much trouble with Kangaxx I have a nice Somerset Brie that might help.
Unfortunately I don't have the ioun stone to raise Imoen's intelligence to 18 yet. Which is why I have yet to memorise the spell. I know there is another scroll in Sundesallar but that's in Chapter 7. XD
Go to a temple (any temple in Athkatla for instance)
Buy a Potion of Mind Focussing. Have her drink it.
No, once it's scribed into your spellbook you're fine, intelligence only affects what level of spell you can scribe (and possibly casting failure) just buy lots of potions of genius and mind focusing that way you can memorize spells whenever you want, plus you can use them as INT restoring potions if you're ever fighting mind flayers.
Comments
Buy a Potion of Mind Focussing. Have her drink it.
Have her learn the spell.