Praise be to Allah.
Removing the pubic hair by plucking or shaving is one of the sunnahs of the fitrah which are encouraged in Islam, as al-Bukhaari (5441) and Muslim (377) narrated from Abu Hurayrah that the Prophet (blessings and peace of Allah be upon him) said: “Five things are part of the fitrah: circumcision, removing the pubic hair, clipping the fingernails, plucking the armpit hair and trimming the moustache.”
The Prophet (blessings and peace of Allah be upon him) set a time frame for his ummah, that they were not to leave doing that for more than forty days, as it is narrated by Muslim (379) from Anas: He set a time for us to trim our moustaches, cut our nails, pluck our armpit hair and shave our pubic hair; we were not to leave that for more than forty days.
Al-Mubaarakfoori said in Tuhfat al-Ahwadhi: al-Nawawi said: what this means is that we should not leave it for more than forty days, not that he set the time for leaving it as forty days. And he said: What is preferred is to do it according to need and length; if it grows long then he should shave it. End quote. Al-Shawkaani said: Rather what is preferred is that it should be limited to forty days as days set out by the Messenger of Allah (blessings and peace of Allah be upon him) and it is not permissible to go beyond that. It is not regarded as contrary to the Sunnah if one does not trim the moustache and so on after they grow long until the end of that period. End quote.
There are two reservations about what is mentioned in the question about leaving the pubic hair and making it into the shape of a heart as a kind of adornment for the husband.
Firstly: If that means going beyond the forty days without removing it, that is contrary to the command of the Prophet (blessings and peace of Allah be upon him).
Secondly: This site is the extreme ‘awrah which it is not permissible to uncover except in case of necessity or urgent need, so it is not permissible to uncover it for the hairdresser or cosmetician merely for the purpose of adornment.
Muslim (338) narrated that Abu Sa‘eed al-Khudri said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “No man should look at the ‘awrah of another man, and no woman should look at the ‘awrah of another woman.”
Al-Tirmidhi (2794), Abu Dawood (4017) and Ibn Maajah (1920) narrated from Bahz ibn Hakeem from his father that his grandfather said: I said, O Messenger of Allaah, with regard to our ‘awrah, what may we uncover of it and what must we conceal? He said: “Cover your ‘awrah except from your wife and those whom your right hand possesses (i.e., concubines).” I said, O Messenger of Allaah, what if the people live close together? He said, “If you can make sure that no one sees it, then do not let anyone see it.” I said, O Messenger of Allaah, what if one of us is alone? He said, “Allaah is more deserving that you should feel shy before Him than people.”
This hadeeth was classed as saheeh by al-Albaani in Saheeh al-Tirmidhi.
Al-Nawawi (may Allah have mercy on him) said in Sharh Muslim: The words of the Prophet (blessings and peace of Allah be upon him), “No man should look at the ‘awrah of another man, and no woman should look at the ‘awrah of another woman. No man should lie with another man under the same cover, and no woman should lie with another woman under the same cover” indicate that it is haraam for a man to look at the ‘awrah of another man and for a woman to look at the ‘awrah of another woman. This is something concerning which there is no difference of opinion. Similarly it is haraam for a man to look at the ‘awrah of a woman and a woman to look at the ‘awrah of a man, according to consensus. The Prophet (blessings and peace of Allah be upon him) referred to a man looking at the ‘awrah of a man and a woman looking at the ‘awrah of a woman, so that (looking at the ‘awrah of the opposite sex) is even more haraam. This prohibition applies in the case of people other than husband and wife; in the case of husband and wife, each of them may look at the entire ‘awrah of the other. End quote.
See: Fath al-Baari, 9/338, 339
And Allah knows best.