The analysis of all known references to Jewish female names in England and Northern France leaves no doubt that בלשת (also known in France) is the same name that the one spelled Belle-Assez or Belaces in various other document written in Latin characters. The transliteration from Hebrew to Latin characters would be purely formal, according to the conventional rules you decide to use (for example, blšt). If you mean (phonetic or morpho-phonetic) transcription rather than transliteration, then you could, for example, write
*Belases (בלשת), *Belaseth (בלשת), or even *Belle-Assez (בלשת).