It's not like it wasted anything. A little extra effort in finding a scroll for the spell, a little time spent finding space in one of her many spellbooks and categorizing it, a little overhead for when she was looking for a specific spell.
But one of the benefits of the particular skill tree she'd chosen was the ability to cast anything, as long as she had the spell written down. Sure, she could only cast it at level one with the bare minimum of spell effects, but having that kind of versatility, that kind of access to whatever she possibly needed – that was definitely something.
Not something that often paid off, but it was worth the effort for moments like this.