I started out getting a little pouch from eBay, it's fairly small, the first photo is the pouch next to a paperback book to give you some perspective.
The next picture is side one to show the thickness. It's fairly wide once packed, but it only weight about 1kg. She carries a fairly big shoudler bag to work (that honestly has more crap than anything else) so will be no bother to carry. You can see a whistle, flash-light and paracord braclet attached to the back and zips for ease of access.
This is all the contents of the pouch.
From top left moving right ... Paracord braclet, whistle with a compass, thermometer and magnifying glass on it, aluminium torch, small first aid kit with a tenner strapped to to it, rehydration/dihoreha power x2, small sewing kit x2, ladies products x2, space blanket, Draper multitool (which has a blade under 3 inches so it's legal to carry), sanitiser pen, chewing gum, lighter and bandana (to be used as a sling, face mask etc etc).
And this is the contents of the little first aid kit. A tenner. Heh. Elastic band, cotton wool pads x2, super glue, cotton buds x3, tin, cold and flu tablets x4, nurofen x4, packet of safety pins and small paper clips, large paper clip, antibacterial wipes x2, surgical blades x2, Lightning McQueen plasters x4 (in case my little boy gets a cut), blue plasters x2.
All in all it cost me £16 to put together (£26 if you include the tenner that I put in for her to be able to get home/hospital/wherever in an emergency) and the most expensive thing was actually the pouch at £3.99.
I actually started planning it a couple of weeks ago, and am kicking myself I didn't get it finished sooner. 2 days ago my wife was crossing the road when some effing idiot driving like a moron clipped her. "Luckily" he only hit her with the wing mirror, which came clean off (and then he just buggered off), and she hurt her arm. Her arm wasn't broken but it was very sore and she didn't have a sling or anything (she's a qualified first aider) to secure her arm till she got to the hospital and had I been a little quicker she'd have had a sling (bandana), safety pins and pain killers.
But it's done now .... let me know where I can make improvements, but please be gentle .... I'm still very new to this.
Cheers