To me the i in girl sounds more like curl and hurl. I hope this helps.

double LL is pronounced differently than ( L) because of the vowel sounds.

Yes the letter "l" is pronounced the same in the word girl and the other listed words, you are confusing it with the individual sound the other letters make in the words. But when we look at the word girl the letter L is less emphasised when saying it, compared to saying doll or ball, when we pronounce those words we put more stress/sound on the letter l and the end of the words. Hope it helps. Happy learning😀