La nin gvidinta amikino atendas ĉe la stacidomo.

Gvidinta is the active past participle of gvidi (to guide).

It breaks down like this:

• gvid- = guide
• -int- = having done, having already completed the action
• -a = adjective ending

So nin gvidinta amikino means the female friend who guided us or more literally the female friend having guided us.

Because Esperanto can use a participle instead of a relative clause.

These two are very close in meaning:

• La nin gvidinta amikino atendas ĉe la stacidomo.
• La amikino, kiu gvidis nin, atendas ĉe la stacidomo.

The first version is more compact. The second may feel more familiar to an English speaker.

In this kind of participial phrase, the participle works like an adjective modifying the noun, and its object is often placed before it.

So:

• nin gvidinta amikino = friend who guided us

A very literal word-for-word shape would be something like the us-guided friend, which sounds strange in English but is normal Esperanto structure here.

If you want a more English-like order, Esperanto often uses a relative clause instead:

• la amikino, kiu gvidis nin

Because nin is the accusative form of ni.

Here, we/us are the direct object of gvidi:

• she guided us

So Esperanto uses nin, not ni.

Because amikino is the subject of the main verb atendas.

She is the one who is waiting:

• La ... amikino atendas = The ... female friend is waiting

The direct object in the sentence is nin, not amikino.

That comes from -int-.

The participle gvidinta shows an action completed earlier than the main action or situation. Since the main verb is atendas (is waiting), the sentence means that the friend guided us earlier and is now waiting.

So the timeline is:

1. she guided us
2. she is waiting at the station

Because -in- is the Esperanto suffix for female.

So:

• amiko = friend
• amikino = female friend

The sentence specifically says that the friend is female.

It applies to the whole noun phrase:

• la nin gvidinta amikino

That means the female friend who guided us.

Esperanto normally uses just one la for the whole phrase, not a separate article inside the modifier.

Because these prepositions mean different things:

• ĉe la stacidomo = at/by the station
• en la stacidomo = in the station
• al la stacidomo = to the station

Here the sentence is just giving the location where she is waiting, so ĉe is a natural choice.

Yes. In Esperanto, atendi can be used either:

• with an object: Mi atendas vin = I am waiting for you
• without an object: Mi atendas = I am waiting

In this sentence, atendas is used without an object, and the sentence only tells us where she is waiting:

• ĉe la stacidomo

It is a compound word.

• staci- = station
• domo = building, house

So stacidomo literally suggests a station building, and in normal use it means railway station / train station.

Compounds like this are very common in Esperanto.