All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ʻalayhi wa sallam, is His slave and Messenger.
This question includes two points:
Firstly: this girl's visits to shrines. If she goes to such places without a valid purpose such as forbidding their visitors from committing Shirk (polytheism) and religious innovations and from believing in superstitions, then it is prohibited for her to go there. If she actually joins them in doing these things, then she must avoid all this, even if her parents become angry with her, as she is not required to obey them in what constitutes disobedience to Allah. The Prophet, sallallahu ʻalayhi wa sallam, said, “There should be no obedience to a created being in what constitutes disobedience to the Creator. Rather, obedience is required only in what is good.” [Al-Bukhaari and Muslim] It is indeed grave to incur the wrath of the Creator in order to please the created! ʻAa'ishah, may Allah be pleased with her, reported that the Prophet, sallallahu ʻalayhi wa sallam, said, “Whoever seeks to obtain the pleasure of Allah by incurring people's wrath, Allah will suffice him from the people, and whoever seeks to obtain people's pleasure by incurring the wrath of Allah, Allah will entrust him to the people...” [At-Tirmithi] Her need to live with her family until she gets married does not justify committing these evils with them. Please refer to fatwa 84942 about the limits of the children's obedience to the parents.
Secondly: her marriage to a Barelvi young man. Such a man is not acceptable as a husband. The Barelvi sect is founded on false beliefs and Shirk practices. Abu Hurayrah, may Allah be pleased with him, reported that the Prophet, sallallahu ʻalayhi wa sallam, said, “If there comes to you one with whose character and religious commitment you are pleased, then marry (your daughter or female relative under your care) to him, for if you do not do that there will be fitnah (temptation/tribulation) in the land and widespread corruption.” [At-Tirmithi] This young man's religious commitment is not pleasing; he is not an eligible suitor for her.
Giving her advice is an obligation. It should not be stopped for fear of adding to her confusion. She should be kindly and gently advised in this regard, and it should be clarified to her that if she adheres to the truth and endures whatever happens with patience, then this is hoped to open all doors of goodness for her and also that Allah, the Exalted, would bless her with a righteous husband who would help her guide her family to the truth.
If it is possible to have a righteous Muslim woman give her advice, that would be better, as it is better that a woman – not a man – calls another woman to Allah to avoid potential Fitnah. It should be noted, though, that it is permissible that a man invites a woman to Allah provided that the conditions of the Shariah are met, such as avoiding being alone with her, and the like.
Allah knows best.