Avia dicit se tunicam laceram celeriter consuere et bene sarcire posse.

Because after dicit, Latin commonly uses an indirect statement construction:

• subject of the reported statement → accusative
• verb of the reported statement → infinitive

So in Avia dicit se ... posse, se is the accusative subject of posse.

It refers back to Avia, so the sense is Grandmother says that she herself is able...

If Latin used ea, that would be nominative, and it would not fit this construction.

Se is accusative.

That is because it is the subject of an infinitive in an indirect statement after dicit. In English we say:

• Grandmother says that she can...

In Latin, instead of that she can, you usually get:

• se ... posse

So se is not the direct object of dicit in the ordinary English sense; it is the accusative subject of the infinitive phrase.

This is the standard Latin accusative-and-infinitive pattern for reported speech or thought.

Break it up like this:

• Avia dicit = Grandmother says
• se ... posse = that she is able ...

Inside that reported statement:

• se = subject
• posse = main infinitive verb
• tunicam laceram consuere et sarcire = what she is able to do

So the core structure is:

• Avia dicit
• se posse

Everything else fills out what she can do.

Because they depend on posse.

Latin possum, posse means to be able or can, and it normally takes another infinitive:

• posse consuere = to be able to sew up
• posse sarcire = to be able to mend

Here both infinitives are coordinated:

• consuere et sarcire posse

So the sense is to be able to sew up and mend.

Yes. That is very normal.

In consuere et bene sarcire posse, the one posse applies to both verbs:

• to be able to sew up
• and to mend well

Latin often places the governing infinitive at the end, after the infinitives it controls.

Both words are accusative singular feminine:

• tunicam = tunic, direct object
• laceram = torn, ragged

The adjective laceram agrees with tunicam in:

• gender: feminine
• number: singular
• case: accusative

So tunicam laceram means the torn tunic as the object of consuere and sarcire.

Because adjectives agree with the nouns they describe.

Since tunicam is accusative singular feminine, the adjective must match it:

• nominative: tunica lacera
• accusative: tunicam laceram

English does not change the form of torn, but Latin does.

They are similar, but not identical.

• consuere = to sew together, sew up
• sarcire = to mend, repair, patch up

So the sentence gives a slightly fuller idea than either verb alone. It suggests not just sewing, but properly repairing the torn garment.

They are adverbs.

• celeriter = quickly
• bene = well

Here they most naturally go with the infinitives near them:

• celeriter consuere = to sew up quickly
• bene sarcire = to mend well

Latin word order is flexible, so adverbs do not have to stand exactly where English would put them.

Latin word order is much freer because endings show the grammatical relationships.

So Latin can write:

• Avia dicit se tunicam laceram celeriter consuere et bene sarcire posse

even though English prefers something like:

• Grandmother says that she can quickly sew up and mend the torn tunic well

Latin often puts an important verb, especially an infinitive like posse, near the end. That does not change the basic grammar.

Because Latin usually does not need one in this construction.

English says:

• says that she can...

Latin often replaces that-clause with the accusative-and-infinitive pattern:

• dicit se ... posse

So the idea of that is built into the construction rather than expressed by a separate word.

Yes, in normal usage here it does.

Se is a reflexive pronoun, and in a sentence like this it refers back to the subject of the main verb, which is Avia.

So:

• Avia dicit se posse = Grandmother says that she herself is able

If Latin wanted to say that grandmother says some other woman is able, it would normally use a different accusative pronoun, not se.

Latin often leaves out possessives when they are not necessary.

So tunicam laceram simply means the torn tunic. Depending on context, it may be obvious whose tunic it is, or it may not matter.

If Latin wanted to emphasize her own tunic, it could use suam:

• se tunicam suam laceram ... posse

But without suam, the sentence just speaks of a/the torn tunic.

Avia is a noun in the nominative singular, and it is the subject of dicit.

So:

• Avia = grandmother
• dicit = says

Together, Avia dicit means Grandmother says.

Yes. Latin allows a good deal of movement in word order.

For example, the adverbs could be placed in different positions without changing the core meaning, as long as the sentence remains clear. Their current placement gives a natural association:

• celeriter with consuere
• bene with sarcire

So the exact order is partly a matter of style and emphasis, not just strict syntax.