Jill Valentine is a Special Operations Agent (SOA) of the Bioterrorism Security Assessment Alliance, of which she is a co-founder and one of the original eleven members, making her a respected and high ranking operative of the organization. She is one of the main protagonists of the Resident Evil series.
(source (includes images except the side by side of Jill and Sienna Guillory, which is from Wikipedia. ))
Suggested costume ideas and sources:
1. Jill (at the end of Resident Evil: Afterlife) with her free will suppressed and a P30 pump strapped to her chest.
This costume is the most complicated, it contains a lot of details and shows A Lot of body-ody-ody.
If you must..
You’ll want a purple body suit, like this one from this random website I’ve never visited until I googled for “Purple Catsuit.”
Then you should go to Michael’s, JoAnn Fabrics, or some other local craft store and find thick black material and wide lengths of leather or faux leather.
Get to work with references (always try to use more than one angle) of Jill and a pile of time and liquor handy.
2. Jill in Raccoon City.
This one is easy, she wears a dark mini skirt, a blue tube top, knee-high brown boots and a batman utility belt. Sometimes she has a gun holster on her thigh, a gun holster over her shoulders, or a white sweater around her hips.
3. Jill as a BSAA officer
This option is more conservative and warm. Although all the pieces are fitted, they’re not TIGHT or revealing. You can wear slim fit khakis or grey pants, a light blue 3/4 sleeve shirt, and then strap some lengths of Velcro (they sell it on a spool and you just cut what you need) in the correct places and finish with the batman belt, gun holsters and a hat. Optional, fingerless gloves.