I would just put windows back on the machine all the way and give her what she wants. Don't push her more by changing a theme or something. She wants windows, then just give her that.
Mind you.. speed wise.. my windows 2000 install was one hell of a fast worker on the old machine, it even beat mepis 8 in shutdown speed, but then 2000 isn't so bloated yet as the windowses nowadays
MX-17.1_x64 Horizon 14-3-2018 * 4.15.0-1-amd64 ext4 Xfce 4.12.3 * AMD Asus M4A785TD-V EVO AM3 * ASUS GF GT640-1GD5-L NVIDIA 384.111 * AMD Proc. Athl II X4 635, sAM3 * HDA ATI SB VT1708S An * 2x4Gb DDR3 1600 Kingst * 22" Samsung SyncM P2250 * HP F2280