All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Muhammad and upon all of his family and companions.
Without performing all the pillars of Umrah it won’t be valid, yet those pillars were mentioned in both Quran and Prophetic narrations and were mentioned by Ibn An-Naqib (May Allah have mercy on his soul) where he said: “The pillar of Umrah are: Ihram, Tawaf (circumambulation around the Ka`bah) Sa’y (Walking forth and coming between Safaa and Marwa for seven times) Shaving…. And whoever left a pillar, will remain in state of Ihram till it is offered.” [Omdat As-Salik vol.1 pp.144].
In addition, the person offering Umrah is prohibited to conclude marriage contract before making Tahallul (Lifting the restrictions of Ihram) otherwise the contract will be null, and this is the adopted opinion of Shafiee’s jurists, whereas Ashribini (May Allah have mercy on his soul) said:”While being in a state of Ihram for offering ritual of Hajj or Umrah whether for a guardian, husband or a wife are prohibited from concluding marriage contract and doing so renders it null for the Prophet (PBUH) said (What means):” One who is in Ihram may not marry, or be given in marriage." [Related by Moslim].”
Hanafi’s jurists are of the view that concluding the marriage while being in the state of Ihram is valid and the prohibited matter here is having sexual intercourse as where stated by Al-Mosilee (May Allah have mercy on his soul) what follows:”During the state of Ihram, a person is permitted to conclude marriage contract, since the Prophet (PBUH) married Maimunah (May Allah be pleased with her)) when he was in the state of Ihram (during pilgrimage).” Besides, the prohibition is to have a sexual intercourse and the like and not for concluding marriage contract as been deduced from the following narration “that the Prophet forbade the Muhrim to get married” [Al-Ikhtiar vol.3 pp.89].
Thus and in accordance to Hanafi’s jurists, if the sexual intercourse took place between spouses, the husband is obliged to offer a sheep for each sexual intercourse and it should be distributed among people at the Makah sanctuary according to Abu Hanifa, contrary to Abu Yousef and Muhammad Ibn Al-Hassan’s (Two of the three eminent Imams of Hanafie’s doctrine) opinions in this regard. Further, he said:” if the husband engaged in a sexual intercourse while being in the state of Ihram for offering Umrah and after circumambulation around the Ka`bah for four times then his marriage contract remains valid because he managed to offer most of the circumambulation, but he is obliged to offer a sheep as it is an act of Sunnah (Offering Umrah).” [Al-Ikhtiar vol.1 pp.165].
In this regard, Ibn Najeem (May Allah have mercy on his soul) said:” Being engaged in a sexual intercourse with the wife after offering circumambulation around the Ka`bah for four times won’t render person’s marriage contract null because he has already offered the ritual of circumambulation rather, he is obliged to offer a sheep.” [Al-Baher Al-Ra’eyq Fee Sharih Kanz Al-Dqa’eq vol.3 pp.19].
Moreover, “The person engaged in sexual intercourse with his wife after going around the Kaaba four times or more, is obliged to offer a sheep and his Umrah is valid.” [Al-Johara An-Niara vol.1 pp.171] for Al-Hadadi.
Therefore, your sister (Questioner’s sister) is obliged to wait till the next Umrah to offer the rituals she missed eight years ago, in order to be able to lift the restriction of Ihram due from the previous Umrah, as well as she is obliged to renew her marriage contract in which both spouses will have lawful sexual intercourse, but if she has already offered Umrah after the one in which some rituals been missed, then it will suffice and there is no need to offer new one.
Finally, we (Iftaa’ Dept.) advise you to refer to Iftaa’ Dept. as soon as possible to review the case in details and to give you the best clarification in this regard. And Allah knows best.