Sigrid Philippi gave a correct answer. Some verbs, such as to love, usually describe states and generally do not take a progressive form (verb + ing). Consult a basic grammar book such as English Grammar in Use, unit 4.

The phrase "Has your sister been having long hair for a long time?" is not grammatically correct because the verb "have" in the context of possession (like owning something or describing characteristics) is typically not used in the continuous tense.

This is a fabulous question because it goes right to the heart of why present participles exist in the English language. To explain this, let's look at a simpler example. Consider these sentences: (1) She is happy. (2) She is being happy. Technically, there is no difference. If one of them is true, then so is the other, so why say "being"? The answer is that present participles create mental images. When the listener hears "she is being happy", he imagines her being happy. He can *see* her because participles create mental pictures. The first sentence does not do that. It merely states a fact. Now let's look at the two sentences. Fundamentally the difference is that "had" = "experience of having", whereas "been" = "experience of being". Sentence #1: "has had that hairstyle" = "has experience of having that hairstyle" Some people have that hairstyle, and some people don't. The sentence means that for a long time, the sister has belonged to the group of people described as "having that hairstyle". It can either mean that that hairstyle has been on her head, or that she has been paying people to put that hairstyle on her head for a long time. Sentence #2: "has been having that hairstyle" = "has experience of BEING a person having that hairstyle". Right away, you see the subtle difference between #1 and #2. The dominant participle in #2 is "being", while "having" is secondary. The image that comes into your mind is of her BEING such a person. Whereas "having" limits attention to the hair on her head, "being" focuses more on her as a complete person. She is THAT sort of person, one having that hairstyle. The sentences mean the same thing and you can use them interchangeably, but one puts the emphasis on her hair and the other puts the focus on the whole person. The second sentence is more conversational, more descriptive, and more friendly. The first sentence gets to the point, just saying what needs to be said without embellishment.

You can say "Has your sister been having that hairstyle for a long time?" in the present perfect continuous, but it’s not the most natural choice in this context. 1. Present Perfect "Has your sister had that hairstyle for a long time?": This form emphasizes the completed action or the state of having the hairstyle over a period of time. It suggests that she has had that hairstyle for some duration up to now. 2. Present Perfect Continuous ("Has your sister been having that hairstyle for a long time?"): While grammatically correct, this form emphasizes the ongoing process of having the hairstyle. However, "having a hairstyle" is typically seen as a state rather than an ongoing action. Because hairstyles are not usually changed frequently (unless someone is actively changing them), using the present perfect continuous sounds awkward. The same goes for "I have loved her": "I have loved her." (Present Perfect) This indicates a state of love that has existed up to the present moment. "I have been loving her." (Present Perfect Continuous) This implies an ongoing action, which sounds less natural in the context of love because love is generally considered a state rather than a continuous action. In summary: The present perfect is more suitable for states or completed actions, while the present perfect continuous is used for ongoing actions. In cases like hairstyles and love, the present perfect is generally the better choice.

For the love example you could use what you said although it might sound a bit odd because English speakers wouldn’t really say it that way. But you could because to love someone is a continuous action, whereas getting a haircut or new hairstyle happens once and then it’s over.