how do I treat this?
It could be a fungal leaf spot and blight such as Alternaria panax. Remove infected leaves and discard. You can use a fungicide to protect leaves that have not been infected. Check the fungicide label for the disease or for fungal leaf spots. Even more important is avoiding moisture on the leaves from overhead watering or misting. Water the soil but not the leaves. Allow the soil to dry before watering. Also make sure there is plenty of air circulation around the plant and it is not in a crowded situation.
https://extension.psu.edu/schefflera-brassaia-diseases
https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-care.htm
I need to repot but I'd like to know what she is
It's a Schefflera, one of the easiest and most attractive houseplants to grow. Here is more:
https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-care.htm
https://www.gardeningknowhow.com/houseplants/schefflera/repotting-schefflera-plants.htm
https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-pruning.htm
https://www.gardeningknowhow.com/houseplants/schefflera/why-is-my-schefflera-leggy.htm
WE HAVEN;T HAD FREEZING WEATHER BUT DOWN TO THE 40’S A FEW NIGHTS. IT WILL BE GETTING MUCH COLDER SOON
It sounds like your Schefflera is bouncing back due to the fresh air and light on your balcony, but with colder nights approaching in Minnesota, you'll want to ensure it stays healthy. Since Schefflera is a tropical plant, it won't tolerate temperatures below 50°F for long. Before freezing temperatures arrive, bring the plant indoors to avoid cold damage. Check for pests before moving it inside, as insects may have settled on it while it was outside. Place it in a bright, indirect light spot and maintain a moderate watering routine, allowing the soil to dry slightly between waterings. Indoors, the air can get dry, so misting or placing the pot on a humidity tray can help the plant thrive. Trim any dead leaves to encourage new growth as it adjusts.
https://www.gardeningknowhow.com/houseplants/schefflera/schefflera-plant-care.htm