英文放牛班

請問下列句子中,
Couldn't she just have called later?

1. 使用 later 應該是指未來的事, 這句是假設語氣的用法嗎?
2. 為什麼會用 have called ?

感謝大家指導.

電話中 ...
A: Can you please take down my contact information instead?
A: My name is Angela.
A: My cell is 0952-717-713, my home phone is 2878-2890 and my e-mail is angieissweet@hotmail.com.
A: Thank you.
A: Bye bye.
B: Bye.
B: I don't think she's sweet at all.
B: Couldn't she just have called later?