Well I am a Turk myself, but I think I know what shalabiya really means. No, it doesn't mean seville (which means Ishbiliya in arabic), shbly is different from shlby. You know these arabic root words are really important.

I think it's borrowed from the Turkish "Çelebi", you can hear its pronounciation in this website https://sozluk.gov.tr/ by putting in the search box. It was used to refer to respected, dignified men, scholars, judges, head of a religious order etc. or any man you think is "serious, respectable with good manners" in Ottoman times. The 5th Ottoman Sultan was even called Çelebi Mehmed, referring to his title from his princehood. He was a really wise, just and dignified Sultan, he is almost the second founder of the empire and his struggle started when he was only 13 until he died at 32.

But Çelebi doesn't mean prince etc. We have many Çelebi nicknamed historic figures, such as Evliya Çelebi who travelled the entire Ottoman country at its territorial expansion and wrote books about his travels. Katip Çelebi, who authored a great report on sociopolitical situation of Ottoman empire.

If the Turkish meaning is retained in the arabic lyrics, the song must refer to a girl who is serious, careful, intelligent with modest clothing and behaviours.