Learn Hardcore Italian: La mia coinquilina frequenta l’università e studia fino a tardi. - My female roommate attends the university and studies until late.

The main exception: with singular, unmodified close family members you usually drop the article (e.g., mia madre, mio padre, nostra sorella).
Since coinquilina isn’t a close family term, you keep the article: la mia coinquilina.

What exactly does coinquilina mean? Is it “roommate” or “flatmate”?

Coinquilina (feminine; masculine: coinquilino) is someone who shares the same apartment/house with you—what many Americans call a “roommate” and many Brits call a “flatmate.”

If you mean someone who shares the same bedroom, use compagna di stanza.
Inquilina means “tenant” (someone who rents from a landlord), not necessarily living with you.

How would the sentence change for a male roommate or for several roommates?

Male: Il mio coinquilino frequenta l’università e studia fino a tardi.
Several female roommates: Le mie coinquiline frequentano l’università e studiano fino a tardi.
Mixed group/all male: I miei coinquilini frequentano l’università e studiano fino a tardi.

What does frequentare mean here? Is it a false friend with English “to frequent”?

Yes, it’s a classic false friend. In Italian, frequentare commonly means “to attend” (a school, a course, classes):

frequentare l’università / un corso / una scuola = to attend university / a course / a school. It can also mean “to hang out at” or “to see/date”:
frequentare un bar (go there regularly), frequentare una persona (to see/date someone). It does not mean “to go there occasionally” in the English sense of “to frequent” as a fancy synonym for “visit.”

Why is there no preposition before l’università after frequenta?

Because frequentare is a transitive verb: it takes a direct object with no preposition.

Correct: frequentare l’università, frequentare un corso.
Don’t say: ❌ frequentare all’università. If you use andare, you need the preposition: andare all’università.

Could I say va all’università instead of frequenta l’università?

You can, but there’s a nuance:

frequentare l’università emphasizes being enrolled and attending classes.
andare all’università can mean “to go to university (as a student)” in a general sense, or literally “to go to the campus” (physically going there). Both are common; choose based on whether you want to highlight enrollment/attendance (frequentare) or the act/state of going/being there (andare).

What’s the apostrophe in l’università doing?

It shows elision of the article la before a vowel:

la università → l’università. Elision also happens with lo/il: l’amico, l’orologio. With prepositional contractions you’ll see forms like all’università (from a + l’).

Why does università have an accent on the last à, and is it capitalized?

The accent marks that the stress falls on the last syllable: uni-ver-si-TÀ. Words stressed on the final syllable are usually written with an accent.
It’s lowercase in general (common noun): l’università. Capitalize only when it’s part of a proper name: Università di Bologna.

When should I use e vs ed?

Use ed (optional) before a word beginning with a vowel—mainly to make the phrase flow better: ed è, ed entra. Before consonants, you just use e. Since studia starts with s, e studia is correct (not ed studia).

Does the present tense here mean she’s doing this right now?

Not necessarily. Italian simple present often expresses habitual actions:

frequenta... e studia... = she attends and (generally) studies late. To emphasize “right now,” use the progressive: sta studiando (adesso).

Is fino a tardi fixed, or can I drop the a?

Both are used:

Standard/careful: fino a tardi.
Very common and perfectly natural in speech: fino tardi. With specific times you keep the preposition: fino a mezzanotte, fino alle due.

What’s the difference between tardi and tardo?

tardi is an adverb: È tardi (It’s late), sono arrivato tardi (I arrived late).
tardo is an adjective: la tarda serata (the late evening), il tardo pomeriggio (late afternoon). Related expression: essere in ritardo = “to be late (running behind).”

Any pronunciation tips for tricky words here?

coinquilina: co-in-kwee-LEE-na (stress on -li-). The qu = “kw.”
frequenta: fre-KWEN-ta (stress on -quen-).
l’università: loo-nee-ver-see-TAH (stress on last syllable).
studia: STU-dya (the -ia often becomes a glide “-ya”).
tardi: TAR-dee. Italian r is tapped/trilled; vowels are pure and clear.

Are there natural variants of the sentence?

Yes, for slightly different nuances:

La mia coinquilina va all’università e studia fino (a) tardi.
La mia coinquilina frequenta l’università e resta a studiare fino a tardi.
La mia coinquilina è universitaria e fa tardi a studiare.
La mia coinquilina resta sveglia fino a tardi per studiare.

Any quick agreement/conjugation pitfalls to watch for?

Match the possessive and article to gender/number: la mia coinquilina, il mio coinquilino, le mie coinquiline, i miei coinquilini.
Match the verb to the subject: frequenta / studia (she), frequentano / studiano (they).