Well, all phones are going to react differently to different kernels. You just never really know how a phone is going to react with a kernel until you try it. Also, just curious, why did you put Mik3D on her phone? I would go with MikG just because it's so rock solid.
At any rate, I would definitely check out the Freedom kernel by lithid. For Mik3D or MikG, you want the universal build. The other two are for different builds of the Synergy rom. Now, under the universal builds, there are four different kinds. Aggressive (undervolts the most), More (undervolts a lot, but not as much as Aggressive), Less and Standard (or stock or whatever it's called). If she's not inclined to mess with this stuff, I'd probably just flash the Less Freedom kernel. It will get her some battery benefit and probably be more stable than Aggressive or More. But it seems like a lot of people run Aggressive without any issues, so you could always try the More kernel.
Hopefully that helps, but honestly I would stay away from Golden Monkey. It hasn't been updated in ages, whereas Freedom is in active development. Chop Suey is pretty decent too, but I haven't messed with it much since my phone likes the Freedom kernel more.