Closely Related: What does "because of the angels" refer to in 1 Cor 11:10?
1. Question Restatement:
In Genesis 3, was Adam present when the serpent was talking with Eve?
Even though it is explicit that Adam was "with / עמה" Eve when they ate the fruit - Neither the Hebrew nor Greek texts indicate that Adam was present with Eve during the dialogue.
It is most probable that Adam was present during the dialogue - but remained silent, while Eve was "standing before him", contending with the Serpent, and later with God.
The only possibility - in the text - where Adam may have been persuaded to disregard what he was commanded - is only if Adam was present during that dialogue.
Note 1: This answer is an inductive argument, asserting there is strong supporting evidence. However, this is also an argument that it is impossible to know for certain.
Note 2: There is no linguistic evidence - in the text - that they had been apart from each other, (i.e., "And Eve brought Adam the fruit ...", etc). See valid Arguments from Silence.
3. Hebrew Terms:
3.1. Certainly, "גם & עִמָּֽהּ / also and with" Indicates that they ate together:
Heb, Genesis 3:6 - גם־לאישה עמה ויאכל
LXX, Genesis 3:6 - τῷ ἀνδρὶ αὐτῆς μετ’ αὐτῆς καὶ ἔφαγον / [they ate, 3P Plural]
Literally. - Also to the man [to her / with her] they/he ate.
Judges 13:9 also uses "with / עִמָּֽהּ" to denote physical presence.
3.2. Certainly, the Dialogue was Between the Serpent and Eve as a Proxy:
NASB, Genesis 3:4 - 4 The serpent said to the woman [הָֽאִשָּׁ֑ה], “You surely will not die!"
NASB, Genesis 3:5 - For God knows that in the day you eat [אֲכָלְכֶ֣ם, third person plural] from it your eyes will be opened, and you will be like God, knowing good and evil.”
4. The Context
4.1. Eve's Role to Stand Before Adam - to Defend and Confront Adam:
NASB, Genesis 2:18 - Then the Lord God said, “It is not good for the man to be alone; I will make him a helper suitable, (עזר כנגדו, Ezer Kenegdo) for him.”
NASB, Genesis 3:12 - The man said, “The woman whom You gave to [confront me / עִמָּדִ֔י], she gave me from the tree, and I ate.”
This texts indicates that Adam relied on Eve to confront him, and hold him accountable regarding decisions - but that in this case, he was persuaded to disregard what he was commanded.
"Ezer Kenegdo", from "עזר כנגדו" - means "Helper before Him". (There is no linguistic precedent to translate "כנגדו / kenegdo" as "Suitable".)
Idiomatic Use: "Standing Before" is an idiom used extensively throughout Hebrew Scripture, to invoke a "legal" sense - to imply: advocacy, accountability, championing another, etc, (Genesis 31:37, Genesis 33:12, etc).
4.2. Eve's Defense, as Adam's Advocate:
NASB, Genesis 2:13 - And the woman said, “The serpent deceived / נָשָׁא me, and I ate.”
In her argument, Eve didn't point her finger back at Adam - and instead essentially pleaded "Entrapment" - acknowledging that they did transgress the commandment - but only because they were improperly lured into doing so - by an angel who should have been advocating for them, (#5 - Below).
As a result: The text indicates that because Eve stood with, but before Adam - mercy prevailed over the judgment of death.