Sort of depends on how old she is, how well she eats and whatnot.
What I did to determine what vitamins I needed was track my food intake in Fitday, an online nutrition and calorie counting program. I looked at a two month average of my nutrition.
It told me I was deficient in certain vitamins despite eating a well- rounded diet. Mainly C, D, E, Calcium, Iron, and potassium.
So choosing a vitamin for me depended on the RDA values for those vitamins. I looked up the RDA for each, and chose one multivitamin that worked for me. Personally, I chose a high-potency vitamin because it had the complete RDA for iron, 18 mg.
You are supposed to choose a vitamin that will be absorbed well, it should say it on the bottle.
Here is a link I found that is more comprehensive: Tips For The Savvy Supplement User: Making Informed Decisions And Evaluating Information
The best multi vitamin is a good clean diet in it self with lots of leafy green vegtables etc. I love trex's idea of having her track her currnet inake on FitDay - Free Weight Loss and Diet Journal this will really help in analyizing her diet which is key to really seeing any significant fat lose. Please have her sign up for the site we can best help her that way with her diet etc.
As for a fat burner for females I find a yohimbine based product to work most effectly on women and addtional side effect is a raise in her libo as well which will have her doing more cardio too. If you are looking for a suggestion I have always have good success with Nutrex Lipo 6X, 240 Multi-Phase Capsules - $57.95 : Orbit Nutrition