Learn Icelandic: Já, hún er frekar víð.

frekar means "rather" or "fairly" and is an adverb of degree modifying the adjective víð. Adverbs never change their endings to match gender or number, so it stays frekar regardless of what you are talking about!

Why is the feminine pronoun hún (she) translated as "it" in this sentence?

In Icelandic, all nouns have a grammatical gender. When referring back to an inanimate object, you must use the pronoun that matches its gender. Here, the speakers are likely talking about a feminine clothing item like peysa (sweater) or skyrta (shirt), so hún simply acts as "it".

What is the dictionary form of the adjective víð?

The dictionary form, which is masculine singular, is víður. Because it is describing the feminine pronoun hún, we drop the -ur ending to get the feminine form, víð.

Does víð literally mean "wide", or is it the standard word for "loose" clothing?

It literally means "wide," but in Icelandic, it is the standard and natural way to describe clothing that fits loosely. If you wanted to say a piece of clothing is tight, you would use the opposite word, þröngur.