Hi disillusioned.
Dissinterest is not you problem.
Fear and ignorance is.

Your partner is you most valuable asset treat her with the care a long term asset deserves.

Discuss the idea of earning enough from investment to not ‘have to’ work. Nothing works like success. Make some.
Too good to be true is probably an idea that someone with less than you might have about your situation. This too is an idea that is too simple to be true for them.

Suggest you put up the payments on your mortgage to reduce the spare money and put further pressure on the spender. Pays your mortgage of sooner too.
No money this week as it is all on our mortage. If partner objects try asking partner to save (ie permanently not spend) the same amount each month that you are paying to the bank as interest.
Good idea to make concrete the profit the bank is making from you. I bet you quietly pay this expence too.

Try this one on your partner if you like a fight.
Write your obituary now
What would you wish people to say about you whey you die. Spent a lot of money in a frivolous and selfish manner. Chose to stay ignorant because it was easier, Perhaps not!
What would you wish to have done before you hit pay dirt 6 feet under.
Sound morbid but this is war.
How much of your life time are you willing to spend in a mediocre way because of fear and ignorance.
First try and put in words what you realy mean. What is it you are wanting. When are you wanting it. When you have this down, look from the partners position. What are you asking that person to give up. They will see it as loosing something they are comfortable with. (Spending 110% of income is not human nature it is just irresponsible) If you are not financially indipendant you can not afford the doodads. If you loose your means of income will the doodads keep you alive or eat you alive?
Risk analysis puts strategies in place to keep you safe when the worst case happens. What are your strategies for surviving the crash?

Look for a carrot that the partner will value.
If you can find one (more is better) you have an powerful negotiating and sales position. Find what they want and look for a way for them to let you give it to them.
Don’t make the mistake (made it several times befor I learned) of telling them what you know. They have already told you they do not want to know. Do not get between them and a comfortable position unless you like a fight. Remember you loose this one when you win.(just hope this does not apply to this advice)

Try moddeling your strategy. Show them the concrete, real time thing. When I do this— I get this —-. This is how easy it can be.
How much of this could you want?

Remember never give in and never give up. It is your life and it is serious. You are going to die from it so make it something you are willing to die for. Nothing else is enough.
Practice making your language say what is really happening and what you really mean and what you really want and when you would like it. Partner will understand you better and you never know that person might like you better if you were more masterful with your self. Honesty pays dividends.
Good luck favours the prepared and pasionate life.
I hope you get more dissillusioned, think about it! If you are living in an illusion would you not want to wake up from it? You probably just feel uncomfortable loosing your comfortable position. Sound familiar?!
Which will it be the red pill or the blue one.
May you live in interesting times.
Ratty