She wants to cut off all desire and never get married

Firstly: 

Allah, may He be exalted, has created sexual desire in humans because of the great benefits that result from it. 

The Prophet (blessings and peace of Allah be upon him) forbade castration and celibacy that deprive a person of permissible pleasure. The scholars drew an analogy between that and everything that leads to prevention of desire and producing offspring altogether. 

As-San‘aani (may Allah have mercy on him) said: 

… They were unanimously agreed that cutting of the penis and castration are prohibited, and they included with that anything that comes under the same heading.

End quote from Subul as-Salaam (2/160) 

Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him) was asked: is it permissible for a man take medication in order to reduce sexual desire? 

He replied:

There is nothing wrong with that, but it is not permissible for him to take any medication that will stop it permanently. As for reducing it, there is nothing wrong with that, because that serves an obvious purpose. The Messenger of Allah (blessings and peace of Allah be upon him) stated that fasting reduces desire, in the hadith in which he (blessings and peace of Allah be upon him) said: “O young men, whoever among you can afford it, let him get married, for it is more effective in lowering the gaze and guarding one’s chastity. And whoever cannot afford it, let him fast, for it will be a shield for him.”

End quote from Majmoo‘ Fataawa Ibn Baaz (21/188) 

See also questions no. 126987 and 127165  

Removing the clitoris altogether is not permissible, because it weakens desire severely or takes it away altogether. Rather what is prescribed in this regard is to cut a small part of it so as to moderate desire. This is the teaching of the Messenger (blessings and peace of Allah be upon him), as has been explained in the answer to question no. 9412. 

With regard to your resolve never to get married at all, this is inappropriate because the ruling on marriage – for young people – is that it is either obligatory or recommended, and it is an act of obedience to Allah, may He be exalted, according to either opinion. Some of the scholars regarded it as an obligatory act of obedience, and others regard it as encouraged but not obligatory, but it is obligatory in the case of one who is overwhelmed by desire and fears hardship or falling into that which is haraam, as appears to be the case in your situation. We have explained this in the answer to question no. 220841  

Marriage leads to many benefits and good things that are missed out on by the one who does not get married. Hence marriage was the practice of the Messengers. Allah, may He be exalted, says (interpretation of the meaning): “And indeed We sent Messengers before you (O Muhammad blessings and peace of Allah be upon him), and made for them wives and offspring” [ar-Ra‘d 13:38]. 

You may think that the time is not right to take this decision (concerning marriage), but it will be appropriate at the right time, in sha Allah. It is sufficient that it will protect you from this sin that you are doing, namely masturbation, and this is the prescribed remedy for this sin, not what you want to do. Hence the Prophet (blessings and peace of Allah be upon him) instructed young people to get married, and he said: “…it is more effective in lowering the gaze and guarding one’s chastity.” Narrated by al-Bukhaari (5065) and Muslim (1400). 

Our advice to you is to accept the idea of marriage, now and not at some other time, and to seek reward in it by means of good intentions, such as maintaining chastity, obeying the husband and raising children, and so on. 

We ask Allah, may He be exalted, to enable you to do all that is good. 

And Allah knows best.