"she proves very serious"?
"This year as well, she proves very serious"

I'm not sure, is it grammatically correct?

If that's the case, then, is it optional to use "to be" following the verb "to prove" as:
"She proves to be very serious"?
That's how I learnt how to use this verb.

Thanks for your answer!

Question

"she proves very serious"?
"This year as well, she proves very serious"

I'm not sure, is it grammatically correct?

If that's the case, then, is it optional to use "to be" following the verb "to prove" as: 
"She proves to be very serious"? 
That's how I learnt how to use this verb.

Thanks for your answer!

Answer

"She has proven to be very serious"

This is probably the most frequent form.