I get what you mean by arcane; arcane=arcane, ritual caster=ritual caster.
But I'm not sure what your wife means by "controlling". Does she mean the mechanical "preventing the bad guys from doing what they want to do?" (what is meant by a "controller" in 4e) Or does she mean "taking over the monster's minds and making them do what I want them to do"?
In the first case, I think your best pairing is Cunning Bard/Fighter (with the Agile Opprotunist feat). A well-built fighter is a melee controller with better defenses and near-striker level damage, so your wife could draw in the bad guys and make sure whatever they do, that she's ready for them. Meanwhile, the most crucial role in groups is a leader; with one, you have a lot of resilence for making mistakes, and with two they tend to act as backups for one another, but a party full of strikers and controllers tends to be very much a glass cannon, with fast deadly combats, but unable to recover from a bad run of luck. So as a bard, you've got some great enabling powers and abilities, and can easily dip other arcane types at need. Meanwhile, in combination--a cunning bard slides his allies whenever they are missed, whereas a character with the Agile Opportunist feat can make a melee basic attack whenever they are slid (as an immediate reaction). So if the bad guys run away, your wife gets to inflict punitive damage and maybe stop them in their tracks; if they stick around and miss her (as they will often do), she gets slid to a more advantagious position and gets to hit back. Win/win -- and a trick that you can't often do in RPGA, as most characters have to play well with any group rather than being designed as a team.
And, of course, playing a bard, you're at least slightly fragile -- so having a fighter to stand in the way can't hurt. And you can use Misdirected Mark to let her mark extra enemies, &c.
Now, if you mean "taking over enemies and making them do what I want to do," that pretty much means a psion, a warlock, or a wizard (or maybe, if she's willing to wait, an avenger, who gets a very nice dominating paragon class). But there aren't that many awesome synergies between most of these and most arcane classes--I'm guessing you don't want a Swordmage (arcane, but not a ritual caster until you spend a feat to do so), so that leaves you with a controller/controller synergy; spec one controller for movement controlling, and another for blasting (genasi or teifling blaster), and you can make monsters' lives miserable, as one of you locks the baddies into a box and the other one sets fire to the box. But while this is awesome when it works (and it works a lot), you'll both be playing pretty fragile builds (easy enough to up defenses, but hp/surges will still be very low), and you won't play well with others as well as defender/controller or defender/leader combos do.