Individual personality is hard to pinpoint just by breed. There are sweet, mild-mannered horses of every breed, just like there are maniacal, crazed horses of every breed.
That being said, Irish Sport horses are bred for the hunt field to have excellent temperaments, to be calm, but will become more lively when asked, and are very tough. Oldenburgs have a variety of temperaments, are courageous and are versatile sport horses. The cross sounds very sporty, and as long as she's not a nut-case and is sound, she sounds like a suitable riding partner. Other factors will determine her personality even further, so there is no way of telling what you will get until you go see her.