Learn Hardcore French: Sa grand-mère est fière quand elle lit leurs lettres sans presque aucune faute d’orthographe. - Her grandmother is proud when she reads their letters with almost no spelling mistakes.

In French, the possessive adjective (son / sa / ses) agrees with the gender and number of the noun possessed, not with the gender of the owner.

grand-mère is a feminine noun.
Singular feminine → sa grand-mère (her grandmother / his grandmother / their grandmother).
If it were grand-père (masculine), you would say son grand-père.

So:

sa grand-mère = his / her / their grandmother
son grand-père = his / her / their grandfather

Why is there an e in fière?

The adjective fier (proud) must agree with the subject in gender and number.

Masculine singular: fier
Feminine singular: fière
Masculine plural: fiers
Feminine plural: fières

The subject is sa grand-mère, which is feminine singular, so we use:

Sa grand-mère est fière = His/her grandmother is proud.

If it were a grandfather:

Son grand-père est fier.

Who does elle refer to in quand elle lit?

In the sentence Sa grand-mère est fière quand elle lit leurs lettres…, the pronoun elle almost certainly refers to sa grand-mère.

Reason:

The only clear feminine singular noun mentioned before elle is sa grand-mère.
So elle lit = she reads → the grandmother reads.

If the context talked about another feminine person just before (for example, sa mère), it could become ambiguous, but with this sentence alone, elle naturally points back to sa grand-mère.

Why is it leurs lettres and not ses lettres?

Both leurs and ses mean their / his / her in English, but they work differently:

leurs = their (letters belonging to several people)
ses = his / her / its (letters belonging to one person)

So:

Sa grand-mère est fière quand elle lit leurs lettres…
→ The letters belong to them (a group), not to the grandmother.

If the letters were written by the grandmother herself, you would say:

Sa grand-mère est fière quand elle lit ses lettres.
(She is proud when she reads her own letters.)

What does quand express here? Is it “when” or “whenever”?

In Sa grand-mère est fière quand elle lit leurs lettres…, quand expresses a habitual or repeated situation.

So it means more like:

whenever she reads their letters
or
when she reads their letters (in general, each time)

French present tense + quand is often used for general truths and habits:

Je suis content quand il fait beau.
= I’m happy when/whenever the weather is nice.

Could we use lorsque instead of quand here?

Yes. You could say:

Sa grand-mère est fière lorsqu’elle lit leurs lettres sans presque aucune faute d’orthographe.

lorsque and quand often mean the same thing (when) and are interchangeable in many contexts.

Nuance:

lorsque is slightly more formal or literary.
quand is more neutral and very common in speech.

Here, both are correct; quand is just more everyday French.

Why is it sans presque aucune faute and not something like avec presque aucune faute?

The pattern sans + (presque) aucune + noun is very common in French:

sans aucune faute = without any mistake
sans presque aucune faute = without almost any mistake / with almost no mistake

Even though both sans and aucune have a negative sense, this is perfectly normal French. It is not considered a “double negative error” here; it’s just the standard way to say without any / without almost any.

You could say avec très peu de fautes (with very few mistakes), but avec presque aucune faute sounds awkward. Native speakers prefer:

avec très peu de fautes
avec presque pas de fautes
sans (presque) aucune faute

Why is faute singular after aucune? Why not aucunes fautes?

In standard French, aucun / aucune is followed by a singular noun:

aucun problème = no problem / no problems
aucune idée = no idea / no ideas
aucune faute = no mistake / no mistakes

So:

presque aucune faute = almost no mistake(s)
(it means plural in English, but stays singular in French)

Using aucunes fautes is normally considered incorrect in standard French (though you might hear it informally).

Why is it faute d’orthographe and not faute d’orthographies?

Une faute d’orthographe is a fixed expression meaning a spelling mistake.

faute is the countable word (mistake).
orthographe is like an uncountable field/discipline (spelling).

So you say:

une faute d’orthographe
des fautes d’orthographe
sans faute d’orthographe
sans presque aucune faute d’orthographe

You almost never pluralize orthographe in this expression. faute d’orthographes sounds wrong to native speakers.

Could we just say sans faute d’orthographe instead of sans presque aucune faute d’orthographe? What’s the difference?

Yes, you can say both, but the meaning changes:

sans faute d’orthographe
→ with no spelling mistake at all (perfect spelling)
sans presque aucune faute d’orthographe
→ with almost no spelling mistakes (maybe one or two small errors, but very few)

So presque aucune softens the idea: it’s not perfectly perfect, but very good.

Why do we use lit (present indicative) and not a subjunctive like lise?

In quand elle lit leurs lettres…, quand introduces a real, factual time (each time she reads the letters), not a wish, doubt, or hypothesis.

After quand used for real time, French normally uses the indicative.
The subjunctive (quand elle lise) would sound wrong here.

Compare:

Je suis content quand elle lit leurs lettres.
(I’m happy when she reads their letters.) → indicative

The subjunctive appears after other conjunctions like bien que, pour que, afin que, etc., but not after quand in this kind of factual, habitual sentence.

Why is it leurs lettres and not something like les lettres d’eux?

In French, you almost never say les lettres d’eux to mean their letters. Instead, you use a possessive adjective:

leurs lettres = their letters
ses lettres = his/her letters

les lettres d’eux sounds unnatural and is only used in very special contrastive contexts (and even then, speakers avoid it).

So the normal, idiomatic way is:

Sa grand-mère est fière quand elle lit leurs lettres…
and not …quand elle lit les lettres d’eux….