All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
A vow is adherence to do a non-obligatory act of obedience to Allah. However, if the conditions of the vow are fulfilled then it becomes binding. The type of the vow mentioned in the above question is a conditional vow dependent upon something happening. The Shafie jurist Al-Shirbini said: "A conditional vow is one dependent on something happening where the person making the vow commits himself to deliver an act of obedience to Allah if a blessing befalls him or he is spared an affliction. This is as when a person says, "If Allah heals my father, I will fast such and such days or free a slave and the like. In this case, the vow must be fulfilled if the condition is fulfilled." {Moghni Al-Mohtaj, Vol.6:p.233}.
Almighty Allah praised those who fulfill their vows where He said {What means}: "They perform (their) vows, and they fear a Day whose evil flies far and wide." {Al-Ensan, 7}. In addition, the Prophet (PBUH) said, "He who vows to obey Allah, should obey Him. But he who vows to disobey Allah, should not disobey Him." [Al- Bukhari]
Moreover, the person making the vow doesn`t have to fulfill it if its conditions weren`t fulfilled. This is since the purpose or the condition upon which the vow is dependent wasn`t achieved, or the person to whom the vow was made passed away before the conditions of the vow were fulfilled. The Shafie jurist Ibn Hajar said: "If the person to whom the vow was made passed away before the conditions or purpose of the vow were fulfilled then the vow is nullified." {Tohfat Al-Mohtajj, Vol.10:p.77}. It is stated in the Shafie book {Boghyat Al-Mostarshideen, p.588}: "The conditional vow is nullified by death of the person to whom it was made before its conditions were fulfilled."
In conclusion, the asker doesn`t have to fulfill her vow since the condition, which is receiving a certain amount of money, was fulfilled after the death of her mother to whom the vow was made. However, if the condition was fulfilled and she received that sum before the death of her mother, but she delayed fulfilling her vow until her mother passed away, then she must give the bracelets to the heirs of her mother. And Allah the Almighty knows best.