Learn Hardcore Greek: Τη βλέπω κάθε μέρα στο σχολείο.

Τη is the weak (clitic) feminine singular accusative pronoun: her. Depending on context, it can also mean it if the referent is a feminine noun (for example, τη γάτα = the cat).

Why is it Τη and not Την?

Modern spelling often drops the final -ν of την before most consonants. A common guideline: keep -ν before a vowel and before κ, π, τ, ξ, ψ and the clusters μπ, ντ, γκ, τζ, τσ; otherwise it may be omitted. Since βλέπω starts with β, many write τη βλέπω, though την βλέπω is also seen and not “wrong.”

Examples:

την άκουσα (before a vowel, keep -ν)
την πήρα (before π, keep -ν)
τη βλέπω (before β, -ν is usually dropped)

Where is the subject I? Why isn’t εγώ used?

Greek is a pro‑drop language: the verb ending on βλέπω (-ω) already shows 1st person singular, so εγώ (I) is omitted unless you want emphasis or contrast: Εγώ τη βλέπω…, not ο Γιάννης.

Can the object pronoun come after the verb? Could I say Βλέπω τη?

No, not in a neutral statement. Weak object pronouns normally come before the finite verb: Τη βλέπω. They appear after the verb mainly with affirmative imperatives: Δες την!, Πες το! With particles like δεν, θα, να, μην, the pronoun goes between the particle and the verb: Δεν τη βλέπω, Θα τη δω, Να τη δω, Μην τη δεις.

What case is τη and why?

Accusative. It’s the direct object of βλέπω (to see), which takes its object in the accusative.