Jane Foster found the hammer of Thor. After some instances of her helping in Asgard against Loki and an alien invasion, she was promoted to a goddess and the hammer was given to Donald Blake, as it was supposed to. Thor got involved with Sif and Jane Foster married Odin.
In the comics everytime Jane became Thor, Mjolnir purged her body of toxins. In her case those toxins were the chemotherapy drugs that were at the very least keeping her cancer in check. So everytime she became Thor her condition became worse.
In the climax of Death of the Mighty Thor, Jane succumbed to her cancer after becoming Mighty Thor to defeat the Mangog, but Thor and Odin were able to revive her by harnessing the power of the God Tempest, the cosmic thunderstorm that dwells within Mjolnir.
While Thor had likely believed there was nothing that could be done to the hammer after Hela destroyed it, the broken pieces of Mjolnir came together as soon as Jane neared them, making the hammer whole again and transforming Jane into the Mighty Thor.
In 2025, Mjølnir reassembled itself in order to bestow power on to Jane Foster, who began operating as Mighty Thor. However, Mjølnir's power prevented any attempts to treat Foster's cancer. After Foster's death, Thor regained possession of Mjølnir.
What If... Jane Foster Had Found -- the Hammer of Thor? | COMIC BOOK UNIVERSITY
Can Jane return from Valhalla?
In the comics, Jane hesitates at the gates of Valhalla, not wanting her life to be over yet, until Thor and Odin combine forces to revive her. With a second chance at life, Jane makes her cancer treatments a priority, and goes back and heals up while Odinson takes up Mjolnir and becomes Thor again.
Stormbreaker has the additional power to summon the Bifröst, allowing Thor to teleport anywhere in the Nine Realms. Screen Rant has identified Stormbreaker as the more powerful of the two, based on this ability, as well as it being a much larger and edged weapon.
When Thor and Jane are still dating, Thor asks Mjolnir to always protect Jane no matter what. This oath alone speaks to the deep connection between Thor and Mjolnir, which rarely finds others worthy of wielding it. To keep its promise to Thor, the hammer calls to Jane telepathically, guiding her back to New Asgard.
In the montage of Thor and Jane's relationship, Thor told Mjolnir to protect Jane no matter what, and we see the enchantment symbol glow. So when Mjolnir saw Jane and sensed that she was sick and dying, it tried to give her a second chance.
With his Infinity Formula that had kept him from aging failing him, Fury was severely weakened but able to incapacitate Thor by whispering something in his ear that immediately made him unable to lift Mjolnir; the Odinson rendered unworthy in an instant.
Why did Thor not make a wish to eternity? Simply because it was said that the first person to reach eternity was granted a wish and Thor was clearly not he first person.
She was adopted by Thor after the death of her father, Gorr the God Butcher. Love is one of few people within the MCU to have the ability to weld Strombreaker, alongside her adoptive father, Thor, and Steve Rogers.
Although she was a mortal, Jane Foster was able to gain entry into Valhalla after succumbing to her cancer, as she had died in battle against Gorr the God Butcher. Once her spirit entered the realm, she would be greeted by Heimdall who would thank her for looking after his son Axl Heimdallson.
Brunnhilde asked Jane if she wanted to become a Valkyrie, and she agreed. So, Jane was upgraded to Valkyrie status and gifted Undrjarn the All-Weapon. Since becoming a Valkyrie, Jane has had a full plate.
Torunn is the daughter of Thor and Jane Foster. She's a member of the Next Avengers. When she was a a child she's been looked after by her mother after Thor leaves on an important mission. After growing up she wants to know who and what is she and whats her father like.
In any case, even if the hammer only called to her because of its original oath to the Asgardian prince, Jane proved time and again in Thor: Love and Thunder that she was worthy of Mjölnir as she committed herself to stop Gorr the God Butcher.
Originally Answered: How did Jane became worthy of holding Thor's hammer in Marvel comics? Mjolnir chose her to be worthy because she said that her heart was stronger than her thunder, and it was—she did save Asgard and threw Mangog into the Sun.
Thor is immortal, and Jane is mortal, and time likely passes very differently for the both of them. Therefore, it is plausible that they broke up because of their vastly different lifestyles.
Operating as the Mighty Thor, she befriended King Valkyrie and defended New Asgard from Gorr the God Butcher, reuniting with Thor in the process. However, continued use of Mjølnir greatly weakened her body, and as a result of her decision to join the final fight against Gorr, she succumbed to her cancer.
In one last push, Thor finally put Bor down with Mjolnir, but at the cost of breaking the hammer—and a subsequent banishment from Asgard. Doctor Strange was able to repair it later by channeling Thor's Odinforce into the shards of the mallet.
Unlike Mjølnir, however, the weapon is not enchanted to prevent those deemed "unworthy" from holding it, making anybody with sufficient strength capable of using the weapon.
Many viewers have pointed out that Thanos was able to lift Stormbreaker without a problem, but this is because the ax isn't enchanted as Mjolnir is. Others believe Thanos lifted Mjolnir (although briefly) and have even argued that he would be worthy of doing so.
