Formal:
* Ela está melhor agora. (This is the most common and neutral way to say it.)
* Ela se encontra melhor agora. (This is slightly more formal than the first option.)
Informal:
* Ela está bem melhor agora. (This emphasizes that she has improved significantly.)
* Ela já está melhor. (This implies that her condition has improved recently.)
* Ela está recuperando. (This means "she is recovering" and suggests she is on the way to being fully better.)
More specific:
* Ela está se recuperando bem. (This means "she is recovering well.")
* Ela está mais forte agora. (This means "she is stronger now.")
* Ela está com mais energia agora. (This means "she has more energy now.")
The best translation depends on the specific context and the desired level of formality.