I knew that Spanish was pro-drop, but my understanding was that it doesn't matter that much if it's included. I've learned that generally the pronoun is used in cases where it's not obvious (like 3rd person singular and maybe plural) or for emphasis. But I still thought that even outside those two situations, you could include the pronoun and it would be alright. It just might make you sound non-native. So that's why I was surprised when Vijay struck it out as if it were incorrect of me to include it.
Also, regarding the tilde, I thought that because está is the 3rd singular (and 2nd polite singular) present tense of estar, you write ésta to distinguish "this". But, I just looked it up on Wiktionary, and apparently that's only the case for the pronoun "this one", while what I used, the adjective, doesn't use any tilde.