Praise be to Allaah.
In the answer to questions no. 10670 and 13966 we explained that the woman whose husband dies has to avoid certain things: going out of the house during the day except when there is a need, and at night unless it is absolutely necessary; wearing beautiful clothes; adorning herself with jewellery and other things; and wearing perfume except when she becomes pure from menses or postpartum bleeding (nifaas), in which case she may use only a little.
The woman who is observing iddah following the death of her husband has to avoid the things mentioned above for the length of the iddah period, which is four months and ten days according to the lunar calendar. This is the iddah for all women except one who is pregnant - in that case, the iddah ends when the pregnancy ends.
A husband's request to his wife never to take off jewellery is not a wasiyyah (will or final request) that has to be followed, because it is a request concerning something over which the husband has no authority. Whether to take off the jewellery or not is up to the wife and no one has the right to force her to do any such thing.
Moreover, following shareeah is more important and takes precedence. Shareeah forbids a woman who is observing iddah following the death of her husband to wear jewellery.
It was narrated from Ali (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) said: There is no obedience (to anyone) if it involves disobedience (to Allah); obedience is only with regard to that which is right and proper.
Narrated by al-Bukhaari (7257) and Muslim (1840).
Shaykh Abd al-Azeez ibn Baaz (may Allah have mercy on him) was asked:
With regard to a will or final request that is contrary to shareeah: should it be carried out? How should the one to whom these instructions were given deal with this will?
Instructions that are contrary to shareeah do not count. If final instructions are contrary to shareeah, they should not be carried out. Only those instructions that are in accordance with shareeah may be carried out. End quote.
Fataawa Noor ala al-Darb, tape no. 420
Based on that, this woman has to take off those bangles during the iddah period, then after that if she wishes she may wear them, and if she wishes she may refrain from wearing them.
And Allah knows best.