Questions & Answers about Ako si spremna, uzmi svoju torbu i idemo.
Because spremna is the feminine singular form of the adjective spreman / spremna / spremno meaning ready.
In this sentence, the speaker is talking to one female person, so the adjective has to agree with that person.
- Ako si spremna = If you are ready (said to a woman)
- Ako si spreman = the same thing, but said to a man
Agreement like this is very important in Serbian.
Serbian often drops subject pronouns when they are already clear from the verb form.
Here, si already tells you the subject is you singular, so ti does not need to be stated.
- Ako si spremna = If you are ready
- Ako ti si spremna is not correct standard word order
If you do include ti, it is usually for emphasis or contrast:
- Ako si ti spremna... = If you are the one who is ready...