Context
Worrying about whether the plan will work out.
Ya se arreglará.
'It'll sort itself out' — the Spanish disposition toward things working out. Very natural.
Breezy, optimistic dismissal of worry — it'll be fine, don't stress, things have a way of working out.
'Ella estará bien' sounds like you're worried about a specific woman. This is about situations, not people.
Context
Worrying about whether the plan will work out.
Ya se arreglará.
'It'll sort itself out' — the Spanish disposition toward things working out. Very natural.
Context
Friends fretting about being slightly late.
Tranquilos, que no pasa nada.
Relax, nothing's going to happen — the great Spanish reassurance. Used constantly.
Context
Someone anxious about a minor problem.
No te preocupes, eso tiene fácil arreglo.
Don't worry, that's easily fixed — solving the problem by refusing to be bothered by it.
Context
Reassurance before a big presentation.
Venga, que va a salir genial.
Come on, it's going to go great — venga as an encourager, the Spanish 'come on.'
Context
Someone worried whether guests will enjoy the food.
Que sí, que sí, no te agobies.
Yes, yes, don't stress — agobiarse is to get overwhelmed by worry. Dismissing the anxiety.