A good place to start looking is Don Mayer's Parachute Shop,
http://www.parachuteshop.com
I bought a Strong 304 seat pack from him, works well in my RV-8, T-28 or T-6. The Strong 314 looks to be geared towards the RV-4 and 8, but for other RVs, you might look at a backpack type. One thing that caught my eye are the prices, oh my how they've gone up! Mine was $1500-ish in 2006; today it would be $2250. Ouch.
If you buy from a vendor like this, it arrives in a big box, ready to go. No assembly required, it has a current pack, just pull it out of the box and strap it on. To be legally usable the chute needs a fresh repack every 180 days by a certified rigger. Look around for a sport drop zone, they'll have guys that can do it.
As far as sizing for your girl, call the vendor, they'll know best...
You might also find a decent used one on Barnstormers; if you go that route you'll want to get a fresh inspection and repack right outta the gate methinks

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