My mom taught me to say the bracha on shabbos candles: "lehadlik ner shel shabat kodesh", but from what I see, no one else says kodesh, am i wrong in still saying it since it was my mom who taught me?

The original wording in the Rambam and all early sources is without the word: kodesh. Rav Ovadia Yosef (Resp. Yabia Omer ii, Or. Ch. 16, 18) writes that accordingly, in general it's preferred not to add it. But there are a few rare modern sources where it can be found, see R. Menashe Klein (Resp. Mishneh Halachot xv, 203, a Hungarian hassid) and R. Moshe Shternbuch (Resp. Tshuvot V'Hanhagot I, 270) who cites that this is the wording found by the Ba'al HaTanya and Siddur Korban Mincha, both Chabad (Lubavitcher) sources. Unless you are sefaradi (in which case you shouldn't say it), apparently you have Hassidic roots, for that is apparently what your mother learned from her mother, so you can continue your family custom of saying: "lehadlik ner shel Shabbat Kodesh".