Salams
In a difficult time, someone offered me $5000 who was a good friend, and said they were giving it purely out of goodness of their heart, no strings, no need to pay any of it back, purely as a gift and never to feel bad about accepting.
They are now asking for some or most of it back, though they haven\’t declared they want it back – they have said they expect I pay most of it back though no given amount specified despite me asking them.
However, I had combined the 5k, with another 5k I had  later on, and I had then used 5k of this money. It is hard to say which was from the gift and which money I already had if that makes sense, it had been mixed with my general savings.
From these savings I paid back a debt of 5k. If I recall I do believe my intentions were using the 5k gifted to settle a debt I had with someone else – but I can\’t be 100% sure.
If the money had been mixed with my overall money, it is hard to say if the money I then spent can be considered my money or theirs – but I did have an intention that the money I am spending though mixed with mine, was from the gift.
What is the verdict on paying the person back ? They are causing me a lot of mental health issues and emotional blackmail.
I already know the general jurisprudential answers – but my specific question is, IF the gift I have used has been mixed with my general wealth and spent from that, even if I had wealth left over , can I consider their gift as having perished / what is my islamic obligation?