Permanacy is a fifth level spell, and assuming she is a 10 level sorcerer, she'd have access to it. That being said, it's be her only fifth level spell assuming that all spell casters don't have access to all their spells in this game.
That is to say, we still need to prepare spells daily for those who aren't sorcerers or bards. You know, chose which spells we want to cast for the day or what not. Just for the sake a balancing, it would be quite powerful if Malkai could fire off any of his fourth or fifth level spells he wants as long as he doesn't tucker out from it.
As for permanently having a summoned creature, given that it's GM fiat I suppose there's nothing stopping g you if you really want it. Still, I'd suggest that you make the process a bit more complex and costly then just using your summon monster and permanacy spell together. I'd say thing since summon monster is an "unusual" thing to be the target of a permanacy, a ritual would need to be conducted. After all, you're binding an outsider to our realm. Even if it was a weak one, that's no small feat. Maybe it could be something Vivian asks the party to help her with or something.