As it turned out, Eir was totally ready for that. As a person who had once died and faced the Consciousness of the universe itself, it wasn't so hard to accept the concept of death and existing without body.
Soon she mastered the teachings of Ancient One and became a full fledged sorcerer. This soon wasn't soon from a normal human point of view though.
Around a century of time was small from a gods perspective but those human who were taught with her were now all dead and there was no sorcerer left in their knowledge.
Now that Eir had learnd everything from the Ancient One, she decide it was time to part ways. Anciant one too wanted to open a proper school to teach sorcery to common people so they both agreed that it was time to say farewell.
During their time together, Eir and the Ancient One were grown together, so Eir told her her own plan of gathering all infinity stones.
Ancient one was first socked of learning this or preted to be socked as she may have already seen the future. But she didn't complain or tried to stop Eir.
As she had come to know Eir character in past century, she was confident that she wouldn't harm innocents or couse trouble even after getting power. As for the time stone, she said she could have it after Eir collectes all other stones.
Eir aggred to it.
As for the oath about keeping time stone from other people. It was okey as the oath was to protect the earth from threats but if Eir could get her hands on other five stones, then there was no harm in her having the sixth too. And Ancient one was confident that with this kind of power in Eir hands, she would use it for the good of people or atleast won't cause harm to them.
And as a deciple of Ancient One herself, she had earned the right to use the eye of agamotto. Becouse no knowledge was prohibited in sorcery, atleast not yet.
As for the title of Sorcerer supreme, Eir didn't get that officially, which made her sad, but knowing future, she was confident that after the Ancient One and doctor strange, both dies, she will be the strongest soul Sorcerer out there, even if that will be far in future.
Well, as a goddess with long life, she should be patient and shouldn't rob fleeting mortals of their momentary pleasure of calling themselve Supreme.
That how she convinced herself not to beg the Ancient one to give her the title of Sorcerer supreme.
Well, other then the title itself, Eir got everything else what she needed from this journey. Teleportation, Astral projection, Clairvoyance, Energy manipulation and universal awareness were the most useful ones what she have learnd. Other then that she also got a pile of knowledge about different dimensions and other things like creating mediums or spells to properly use her soon to be infinity stones.
She also wanted to get her hands of strange's flying cloak but it was too slow for her likes. It's totally wasn't because that cloak totally ignored her and even when she forcefully tried to equip it, it attached itself to Ancient One.
Her pride on her charm as Goddess of life was hurt because of that but seeing her sad, many bird and animals gathered around her, and tried to make her happy, which made her feel a bit better.