Learn Hardcore French: Ces bougies sentent la vanille, et ma mère en est très satisfaite. - These candles smell like vanilla, and my mother is very satisfied with them.

Subject: ces bougies = these candles → plural, so we need a plural verb form.
Verb: sentir here means “to smell (of) / to give off a smell”, not “to feel”.

Present tense of sentir (for reference):

je sens
tu sens
il/elle/on sent
nous sentons
vous sentez
ils/elles sentent

So Ces bougies sentent la vanille = These candles smell of vanilla / smell like vanilla.

Why do we say la vanille and not just vanille after sentent?

In French, you almost always need an article before a noun, even when English doesn’t use one.

With smells and tastes, French typically uses the definite article:

sentir le café = to smell of coffee
sentir la lavande = to smell of lavender
sentir la vanille = to smell of vanilla

So Ces bougies sentent la vanille is the normal, idiomatic way to say These candles smell like vanilla.
Saying *Ces bougies sentent vanille (without la) sounds wrong or very “foreign” in standard French.

What exactly does the pronoun en refer to in ma mère en est très satisfaite?

En replaces a phrase introduced by de.

The “full” version of the sentence would be:

Ma mère est très satisfaite de ces bougies.

Because the first part already mentioned ces bougies, French avoids repeating it and replaces de ces bougies with en:

Ma mère en est très satisfaite.
→ literally: My mother is very satisfied with them.

So here en = de ces bougies (with these candles).

Why is it ma mère en est très satisfaite and not ma mère est en très satisfaite?

Object pronouns like en normally go before the conjugated verb in French (except in affirmative commands).

Order in this sentence:

subject: ma mère
object pronoun: en
verb: est
complement: très satisfaite

So:

✅ Ma mère en est très satisfaite.
❌ Ma mère est en très satisfaite. (wrong word order)

The rule: Subject + (pronoun(s)) + conjugated verb + rest of the sentence.

Why does satisfaite end with an -e?

Satisfaite is an adjective that must agree in gender and number with the subject.

Subject: ma mère → feminine, singular
Masculine form: satisfait
Feminine form: satisfaite

So:

Ma mère en est très satisfaite. (feminine singular)
Mon père en est très satisfait. (masculine singular)
Mes parents en sont très satisfaits. (masculine/mixed plural)
Mes sœurs en sont très satisfaites. (feminine plural)

What is the difference between satisfaite and contente here?

Both can often be translated as happy / pleased / satisfied, but there’s a nuance:

content(e): more general, emotional; happy, pleased
- Je suis content de ce cadeau. = I’m happy with this present.
satisfait(e): more about expectations being met, quality, result; slightly more “objective” or formal
- Je suis satisfait de ce service. = I’m satisfied with this service.

In ma mère en est très satisfaite, the focus is on the quality of the candles, or that they meet her expectations.
You could say ma mère en est très contente, which sounds a bit more emotional/colloquial: she’s really pleased with them.

What would the sentence look like if we didn’t use the pronoun en at all?

Without en, you go back to the full de + noun phrase:

Ces bougies sentent la vanille, et ma mère est très satisfaite de ces bougies.

Grammatically, that’s correct, but it’s repetitive. Native speakers prefer to:

mention ces bougies once, then
replace de ces bougies with en in the second clause:

→ Ces bougies sentent la vanille, et ma mère en est très satisfaite.

Using en makes the sentence more natural and less heavy.

Can we also say Ces bougies sentent bon instead of sentent la vanille? What’s the difference?

Yes, but the meaning changes slightly:

Ces bougies sentent bon.
= These candles smell good (nice), but you don’t say what they smell like.
Ces bougies sentent la vanille.
= These candles smell of vanilla (you specify the scent, but not whether it’s pleasant or not).

You can also combine both:

Ces bougies sentent bon la vanille.
= They smell nicely of vanilla / They smell really good, like vanilla.

Note that you say sentir bon / sentir mauvais, not *sentir bien / *sentir mal for smells.

Why is it ces bougies and not les bougies or des bougies?

The determiner changes the meaning slightly:

ces bougies = these candles / those candles (demonstrative, pointing to specific candles the speaker has in mind or near them)
les bougies = the candles (a specific, already known set, but not “pointed at” like these/those)
des bougies = some candles (indefinite, just “candles in general” or new information)

In English you naturally say These candles smell like vanilla, so in French the closest is Ces bougies sentent la vanille.

Also:

bougie is feminine: une bougie
plural feminine: des bougies
demonstrative plural for both genders: ces → ces bougies

What is the difference between sentir and se sentir, and which one is used here?

In this sentence, we use sentir (without se):

sentir:
- to give off a smell: Ces bougies sentent la vanille. (These candles smell of vanilla.)
- to smell something: Je sens la fumée. (I smell smoke.)
- to sense/feel (physically): Je sens le froid. (I feel the cold.)
se sentir (reflexive):
- to feel (in terms of one’s own state):
  - Je me sens bien. = I feel good.
  - Elle se sent malade. = She feels ill.

Here only sentir is correct:

✅ Ces bougies sentent la vanille.
❌ *Ces bougies se sentent la vanille. (incorrect)