I'm secretly buying a 10k rolex without asking my gf about it
Who gave you the idea to buy a 10k rolex?
My ex-gf who was really rich.
If you are able to afford to buy the watch, then it is fine. You are allowed to spend your money as you please.
I really like rolex's so  this is a good purchase.
It is nice to buy things that you like. Just don't spend so much that you cannot pay your bills and other expenses.