Where is your sister planning on working? Biglaw, non-profit, government? Location? Expectations for appearances vary greatly. Your sister needs to look clean and presentable but I can tell you that plenty of lawyers don't wear that much makeup. It is a conservative field though so any makeup should enhance but not distract. I would find her:

• Tinted moisturizer/bb cream to even out her face- This is going to be a bit of a trial and error process. Take her to sephora and get some samples for her to try. *MLBB color- Find something on the sheer side. Revlon Balm Stains are a good drugstore option. Clinique Black Honey might look good. Btw, in a conservative office environment, red lipstick is a no no. I can get away with it in my office but I wouldn't get it for your sister if she already doesn't like makeup. *brow product- The product will depend on what she is willing to do and the shape of her brows. Anatasia brow wiz might be a good option. Also Benefit gimme brow could be a good and easy solution. *blush- Go with a matte or demi matte finish. Nothing overly shimmery or sparkly. Find something that gives her color but isn't too bright. Tarte has great blushes. On darker skin like your sisters, a berry could look really pretty. *mascara- Any old long wearing black mascara will do. I love Maybelline the Falsies. If her eyelashes aren't curly naturally, definitely get her a curler. *concealer- Touch Eclat isn't going to do a lot if she has dark circles. Maybelline Fit Me and Age Rewind are popular choices. I personally love MAC pro longwear but I don't know how well it works with dry skin. Also my best friend swears by the Tarte CC undereye corrector for her dark circles. *powder- This is to set if needed and for touch ups. I'd just go for a drugstore one. Since she's dry my usual recommendation, Rimmel Stay Matte, probably isn't the best idea.