I have the same issue -
Been friends for 6years now dating for a over a year now. She already knows where the car and her stands and what I've been through with the car and money spent on her. I've told her the car comes first regardless. I've been through more emotionally stress with the car than her.
But now she helps me with the car (From conversions and minor/major modifications. She just help me put coilovers in yesterday) and it's something we can share together also gets her spending time with me too since I work 5 days/wk and she's uni student. I can't stay up late like she does and weekend well I work on the car/car forums. She also comes to cruises with me cause she like to see the outcome and progress of what she's help me with.
I dunno if its something your missus is willing to do but makes her see your point of view on cars, being in your shoes.
