Arianwen, Betsi, Blodwen, Bethan, Branwen, Cari, Cadi, Ceinwen, Ceridwen, Cerian, Ceris, Delun, Eirwen, Eiry, Elen, Elisabeth, Esyllt, Ffion, Gwawr, Gwen, Hanna, Heledd, Lilwen, Mali, Mai, Mari, Menna, Nansi, Nia, Rhian, Sali, Sara, Sian, Tegan, Tirion...
Sorry for any duplications.
Lots of my favourite welsh girls names end in -wen (white) which is lovely but sounds naff with our surname which begins with w :(
Some of the prettiest names sound awful if mispronounced, so might be best to avoid if you're not in Wales/welsh speaking area - thinking of Eleri, Fflur, Eurgain, Llinos, Esyllt, Gwawr.