Welcome to the forum Exist25. May I suggest that the most important relationship to cultivate and seek enlightenment with is the one with your own inner Self - alignment. The more at peace you are, and more familiar you are with your own natural being, the clearer your path is likely to be.
As to your ex girlfriend, you can't fix her. You can't take Tolle's, or anyone's, teachings and get another to buy in just because you saw the value in them. All paths to greater clarity are personal. Pointers, such as in Tolle's books, are quite useful, but it's a personal recognition that brings life changing insight.
My experience with relationships where the significant other has little concern for financial balance has always been problematic. Joint bank accounts under these conditions don't work very well and are always a point of contention. There are possible solutions, but often it's best to pass on the relationship in favor of peace of mind. One solution is find it in yourself to be less sensitive to a partners spending habits and find a way to be okay with the way things are. This never worked for me, however.
Another option is to have separate bank accounts and separate incomes. Normal household bills - rent, food, electricity, etc., and anything that both agree on - is split evenly. Personal income remains the possession of the one who earned it. Personal bills are the responsibility of the one who created the bill. This has worked quite well for me. Of course life is not always simple and a degree of flexibility is required. As a base concept however, it saves a lot of heartache.
If a potential partner cannot agree to this before lives are significantly joined, you may want to consider the wisdom of going forward with the relationship. It's sure to be a point of contention. There are no doubt potential partners out there who hold similar perspectives, and it's well worth the patience to await ones arrival.
What has confused me is Tolle's mention of being the conscious one in the relationship even if your partner is always unconscious (as was very much so for my Ex). Is he saying that you should stay in a dysfunctional relationship and make it a spiritual practice even if the signs to part ways are there?
I don't think he was saying to stay in a relationship at all. First, it's not for him to say, and I'm sure he would agree. I think he's saying: don't get sucked into unconsciousness, even if your partner is. If you are indeed conscious, you will feel the best path to take whether it's to stay or to go. Follow the path that feels the best. And don't beat yourself up for your decision however it comes out. Every moment offers another opportunity to choose a new path or to stay the course.
Exploring how a potential choice feels
is almost certainly going to be the best course. And don't confuse emotions with feelings. Emotion is one type of feeling, but one that is often based in personal belief systems that may be out of step with a broader reality. Feel your way to solutions in the quietude of meditation, or clear present awareness. And make a conscious choice to enjoy the process. Enjoyment is a far better path to clarity than is frustration, anger, and fear.