This passage is about service and bearing fruit, not salvation. Both Martha and Mary were saved as shown in John chapter 11. Mary and Martha were the sisters of Lazarus who was raised from the dead.
John 11:5 Now Jesus loved Martha, and her sister, and Lazarus.
As you can see, Jesus loved Martha, she was saved.
Luke 10:38 Now it came to pass, as they went, that he entered into a certain village: and a certain woman named Martha received him into her house.
39 And she had a sister called Mary, which also sat at Jesus' feet, and heard his word.
40 But Martha was cumbered about much serving, and came to him, and said, Lord, dost thou not care that my sister hath left me to serve alone? bid her therefore that she help me.
41 And Jesus answered and said unto her, Martha, Martha, thou art careful and troubled about many things:
42 But one thing is needful: and Mary hath chosen that good part, which shall not be taken away from her.
Martha was not unsaved, she is the one who invited Jesus into her house. But Mary was more spiritual, she attended upon spiritual matters more than Martha. Martha, like those shown in the parable of the sower allowed the cares of the world to take her away from the more important word of God.
Mark 4:18 And these are they which are sown among thorns; such as hear the word,
19 And the cares of this world, and the deceitfulness of riches, and the lusts of other things entering in, choke the word, and it becometh unfruitful.
20 And these are they which are sown on good ground; such as hear the word, and receive it, and bring forth fruit, some thirtyfold, some sixty, and some an hundred.
Unlike many others, I believe only the seed sown by the wayside are the unsaved in the parable of the sower. It did not take root or spring up into life whatsoever. But both the seed sown on rocky ground, and the seed sown among thorns did take root and spring into life. However, the rocky ground has no root and falls away due to persecution, and the seed sown among thorns gets choked by the cares and distractions of the world. Both are saved, but do not bear fruit. This was Martha. She was a believer, but she allowed herself to be carried away and distracted by the cares and troubles of the world.
But the good ground are those that not only hear the word, but continue in it and bear much fruit. This is Mary. Mary knew that to hear God's word and serve the Lord was more important than the physical world we live in. She was a true disciple.
So, this story is about service, not salvation.
And notice that Jesus says the good part given to Mary shall not be taken away. This refers to God's word. Jesus told us to take careful heed of what we hear. To those that hear his word and attend to it, to those more shall be given. But to those who do not listen, even that which was given them shall be taken away.
Mark 4:24 And he said unto them, Take heed what ye hear: with what measure ye mete, it shall be measured to you: and unto you that hear shall more be given.
25 For he that hath, to him shall be given: and he that hath not, from him shall be taken even that which he hath.