I was thinking the same thing. I actually speak Spanish really well and I'm only playing this just for the heck of it. I was thrown off when I was counted wrong for translating it that way.
"She'll start tomorrow." or "She will start tomorrow." should be a perfectly acceptable translation for this.
I thought it was "she begins in the morning." So that's a help to know the "la" differentiates between morning and tomorrow
I'm unsure as to why in DL Spanish you can't use the present tense of "she/he/it is starting" whilst in DL French and Italian you can. It is certainly one aspect of the present tense in English e.g. I start, I am starting, I do start. is there a valid grammatical explanation ?