I think if you have 1K cores saved up, its a decent trade off.
I have no idea about the stats for the Artillery, but M3 seems good for fast "up your face" unit. I use on or two of those and in the right situation it can be pretty useful. Plus she deals AoE in front of her.
Again, no idea about the other girl, didnt find her on Wiki so not sure if she is worth it. But since you are willing to spend the cores anyway you will get her regardless.