I'd say you're on the right track with the idea that you'll want to make sure her main food is the kibble and mealies are just as a treat. My other thought is that, since she's new to your home, try and keep her food pretty similar to how she had it before you brought her home (unless there was something dangerous in her diet before)... at least over this first week or two.
Over time, you'll figure out how many mealies are good amount for her. For example, I learned with Satin, that she'd eat as many as you'd give her, but more than 4 or 5 would turn her poop messy. She was also a touch chubby, so we'd go with 3-4 every 2-3 days. Tex, on the other hand, ran away from mealies as if in fear for his life, so he got 0.
For now though, I'd give her a few days off the mealies so you can see her "regular" poo & behavior vs her "mealies added" poo & behavior. And, over time, you'll figure out the right amount. Maybe start 3 or 4-ish and go from there.
On the topic of her regular diet, I'd also recommend adding in another kibble to the Spike's -- not this week, but maybe starting next week. Many hedgies feel stressed out making the transition into their new homes and have green, mushy, or sticky poo -- so we try and keep things similar to how it used to be for awhile.
In general, it's good to have more than one kibble to try and even out anything that's missed by one nutritionally-speaking. Also, if one kibble changes formulation (ingredients or shape) and hedgie decides "I don't like this anymore" or you run out, then you have the other one to fall back on until you can figure out how to replace the other half of the mix. Depending on who you talk to, you'll find varying numbers of kibble in the mixes - some people choose two kibbles, some choose 3, others have more.