بسم الله الرحمن الرحيم
Wa alaykum salam
There's a few important things to note: Firstly, according to the majority of scholars, zakah is not due on a lady's jewellery if the intention is for it to be worn (regardless of how frequently or rarely she actually wears it).
Zakah only becomes due if the jewellery is clearly a luxury item (meaning that its value is above and beyond what is customary, i.e. if it is deemed excessive) or if the jewellery is an investment asset (i.e. jewellery that is not actually intended to be worn) or if it is intended for resale.
Secondly, when you do your zakah calculation, debts and liabilities have to be taken into account. As such, if you have some jewellery and little or no savings of cash (and no other form of regular income), but on the other hand you have outstanding and/or upcoming bills that need to be paid, those liabilities will be subtracted from your 'zakatable' assets and, as a result, the final sum of those assets may fall below the nisab value — thus, you would not have to pay zakah.
In fact, in your situation you might actually be eligible to receive zakah donations. One of the categories of people that can receive zakah in the sacred law is al-faqir (sometimes also termed al-miskin, depending on the madhhab), and that would be someone who struggles to make ends meet; somebody who may still have food on his plate and a roof over his head, but he or she has really fallen on hard times.
In order to determine whether you fall into that category or not, what you should do ideally is look for a person that you feel you can trust, somebody that has sufficient knowledge on zakah calculations, and who has studied with reliable teachers. Then you talk to him, in person, about the details of your financial situation and together you determine whether you owe zakah or whether, in fact, you may be able to receive zakah donations. Together you will be able to determine in detail exactly which of your present and upcoming liabilities can and should be taken into account and which shouldn't. Additionally, the links further down below will hopefully provide some essential info.
The internet is a great platform to share information, but it is also a means of putting out our (often misinformed) opinions at no more than a mouse click, so take in people's responses on platforms like these with at least a grain of salt.
I think this should answer both parts of your question (and with the above in mind, investing in diamond jewellery is actually counterproductive as it might constitute an asset or luxury item). Besides that, there's one additional point I'd like to mention:
"It is not God's will to cause you distress; rather, it is God's will to make you pure." (Qur'an 5:6)
Often times, certain rules in Islam are meant to challenge us. That is because our nafs, our lower self, and our worldly desires, which all of us have to some extent, are meant to be tackled. If done with the right intentions and the right measure, in overcoming our lower self and our attachment to worldly comfort and pleasures, we draw closer to God, our hearts and souls are purified, and our personalities become more refined.
On the other hand, however, those rules and regulations are not meant to make our lives utterly unbearable or make it impossible for us to survive. In fact, that would be against what are called the maqasid (Ar. مقاصد), the 'underlying principles' or 'underlying objectives', of the sacred law, one of which is the protection and preservation of life.
https://www.islamweb.net/en/fatwa/143267/, https://www.islamweb.net/en/fatwa/82925/zakah-on-womens-jewelry, https://www.islamweb.net/en/fatwa/83665/zakat-on-ornaments
https://youtu.be/alJWwD9wuuA (This last video gives a good general overview on zakah-related questions and reiterates the question on jewellery at 36:30 min.)