How much money should I make this woman pay for a portrait?

What I would do personally is.... Charge about $20-30 more than what you'd usually charge for your "bs" artworks since you are actually making an effort on this now then add a small fee for the materials not the whole cost of the materials since you are not using all of them on the whole piece (unless you actually do use all of the materials up.) So I would say $75 - $127. <--- As you said you usually sell the "bs" artwork for 50- 100 U.S.D so I added $27 for your extra labor. Then maybe add and extra $8 for the used materials.