<human>: Can you condense the text into a few key points?

My girlfriend and I are both 23 y/o and have been dating for 5 years (since high school)

I am currently in massive debt from going through dental school and really cant see myself affording an engagement ring with anything over 1 ct. My girlfriend has always wanted her mothers 3 ct diamond that was used in her previous engagement ring, which was thought to have been lost and was replaced. I really love the stone and would love to design some sort of setting to put it in, which her mother has offered to me multiple times. However, I know that stone in no way reflects my current finances and might be a little overboard.

I know the ring isn't about size and is all about the thought, but to me its not the stone that really matters, I just happen to think its pretty impressive (and free.)

From a female's perspective what are your thoughts? Should I go the route of paying for a diamond myself and working for it, or should I accept her mother's stone and thoughtfully design a band myself?
Male's perspectives welcomed as well!
<bot>: Should I use my girlfriend's mother's 3ct engagement diamond (free) and design a band or should I choose and pay for a ring myself?