You can keep any name as long as it is one with a good meaning - from the meaning you have given there is no problem with keeping the name Liba as the meaning you have stated is beautiful.
Some names are names of Islamic individuals these include the Prophets, angels, Awliya etc. And some names are such that they define an attribute. Like for an example Bahadur, Jameela, Habib, Jaseem, Bassam etc these names are with good meanings and you can keep them infact such names are keep by all people irrespective of their religion. Like you can have someone called Bahadur Ali and you can also have someone called Bahadur Varma or Jameela Ali and Jameela Masih.
There is no problem with keeping a name that defines an attribute as long as it is a beautiful and good attribute. It is not good to name a child with a name that is a bad meaning. Here are some guidelines to follow:
1. We must certainly avoid names that indicate any trace of shirk or association of partners with Allah. Donot use names like Shahensha or Badshah as such names are filled with pride. This is supported by the hadith that reads, "The most detestable name for Allah in the Hereafter is that of a man who calls himself "King of All Kings", for Allah is the Lord of the Kings." (Reported by Al-Bukhari, Muslim, Abu Dawud, and At-Tirmidhi)
It is also prohibited to use the Attributes of Allah with a definite article, such as "Al-`Aziz" (the All-Powerful) and "Al-Hakim" (the Most-Wise), as names. But they may be used without a definite article, e.g. "`Aziz" and "Hakim". You can call a person 'Aziz' but not 'AL Aziz'.
2. We must also avoid names that imply meanings that are offensive or unpleasant in connotations. The Prophet changed names such as Harb (War) with Salam (Peace), ‘Asiyah (Rebellious) with Jamilah (Beautiful), Sa`b (Difficult) with Sahl (Easy to deal with), etc.
3. We are encouraged to give names that have good or noble meanings or associations, for names may inadvertently inspire a person to do great things or stay away from vices. Choosing names of prophets or great persons who have been role models of virtue and piety is an excellent idea. The Prophet (peace and blessings be upon him) named his son Ibrahim, and he said, “I have called him by my father’s name!”
Infact even the names of our Masters the Ahlelbayt of the Prophet also have beautiful meanings eg: Hassan means excellence and pure goodness, Muhammad means one worthy of praise etc.
Also most of the names of early believers were linguistically names of plants, such as "Talhah", "Salamah", "Hanzalah"; names of animals and birds, such as "Asad", "Saqr"; names of objects and parts of nature, like "Bahr", "Jabal"; adjectives used as names, like "`Amir", "Salim"; The point is that you can choose any name as long as it is not holding a derogatory meaning and if it is not in direct association with something evil or Kufr. Like do not name your children after idols or after enemies of Islam like Lat, Uzza, Yazeed, Abu Jahl etc I think this is obvious apart from that give whatever name you like to your children.
So logically there is nothing wrong with the name you have suggested at all. May Allah bless your niece with a lovely life and fruitful knowledge and make her coolness for the eyes of her parents and family.
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