Jennette McCurdy explains why she was 'jealous' of Ariana Grande

"So now, every time she misses work, it feels like a personal attack."

ennette McCurdy is opening up about her working relationship with her "Sam & Cat" co-star Ariana Grande

According to Entertainment Tonight, in her bombshell new memoir, "I'm Glad My Mom Died,"

the ex-actress detailed why she was "jealous" of her co-star during their time on the one-season

Nickelodeon sitcom, and revealed the moment when she reached her breaking point.

McCurdy famously starred as Sam Puckett in "iCarly," while Grande appeared as Cat Valentine in "Victorious,"

and the two reprised their roles in the spinoff "Sam & Cat," which ran from 2013 to 2014.

Jennette, now 30, shared the several reasons why she had feelings of jealously towards

Ariana, now 29, including how the latter was allegedly permitted to "regularly" miss filming

"Sam & Cat" in order to fulfill obligations in her music career, such as

to "sing at award shows, record new songs, and do press for her upcoming album."