Yeah, I thought that with a full-time job taking care of two kids it might be in her better interests to spend the money on a weekend getaway without them.
I will say, to give you some optimism as you continue working on this like it sounds like you're going to, that asking for gifts in advance can be a step up from in-the-moment spontaneous spending. The habit gives the person the chance to think about why they want something rather than being totally wrapped up in the emotion of wanting it. And it delays purchases, giving your money a little bit more time to grow, as well as, hopefully, decreasing the total number of purchases.
So for example if she expresses a desire for something that you consider a big purchase, you could say, sure, hon, we could get that for you for christmas/birthday/valentine's, etc., whatever the next upcoming thing is. That satisfies her immediate desire because you've said yes. Then she's pleased for the whole month or whatever time is left before the holiday because she's enjoying the anticipation of getting the thing. Whereas if she makes an impulse purchase today, it will immediately start to lose its novelty and she'll probably want something else before the month is out.
In other words, I think your plan of talking out how to afford something is a good one. Just make sure the conversation remains positive and that she's getting what she wants more often than not. Otherwise, the impulse spender dreads a "talk" about a purchase that always turns into her not getting it, creating an even strong impulse to just get what she wants right away before discussion can "ruin" it.