Betty Brant

I think because in the comics at the time Glory was Jonah's secretary and Betty was a reporter. It's funny because Betty's Husband Ned Leeds from the comics is in the show. Plus maybe because they wanted different love interests for Peter like Felicia Hardy and Mary Jane. In the comics Betty Brant couldn't be the love interest because she worried about the risks Peter took taking pictures of Spider-Man. She could never know that he was Spider-Man which is why she didn't become his true love. Though then again Gwen Stacey hated Spider-Man because of what happened to her father so I guess that never would've worked out either. I guess Mary Jane was destined to become his love interest in the comics.

"You know Parker, I don't think I've made you suffer enough." Green Goblin Spidey TAS