Sar - she does sound worth it - I'd speak to her about offering her X hours a day and livery for her next horse. With her experience she sounds like she could be good backup for when you get a more experienced person in at a later stage and then you would have the work for her to be full time.
Measles - that sounds like a super job!
I have to say when I was looking for a job the main reason I took the one I did was because I could have my broodmares here too. So although my wage isnt great (given the work and responsibility) I do get grazing for my mares and foals too. So for me it wasn't the wages as much as the flexibility of having my own horses here
Are you looking to take this girl on in your new yard in a similar or different capacity? If she is someone you specifically want as an employee and the purpose of hiring her now is to keep her available? Does she have specific skills or abilities you think are worth paying for? Or is she just someone to fill in the gap?
I agree (for what I know) your arrangement sounds a pretty good deal for a competent but relatively inexperienced person. The only thing I wonder about is the addition of breaking the young stock as a "perk". Surely if she is really good at a specialised skill like this (she's a bit young, in my opinion, to have tons of experience and credentials but not knowing her background I can't say, obviously) she is in a better position to deal a bit as she will be in demand. If she's not so experienced (no matter if she enjoys it or not) are you sure she's the person you want fundamentally responsible for making your young horses? Especially since it sounds like you're planning to hire someone in the next few months who rides at a high standard for your new yard? Are you looking for someone to assist you or to take complete responsibility on their own?
When I was young and used as "cannon fodder" I worked for the experience and helping more knowledgeable trainers break horses really was an attractive proposition. As I got more experienced and was ultimately expected not only to take ultimate responsibility but to produce the horses to a high standard, including getting them in the ring and/or sold, I was paid for my relatively more valuable time and knowledge. So it depends what you're offering this girl and what she needs to do for her career at this point. If you're offering an opportunity, not just a job, then obviously money can be a lesser motivation. If you're just offering a job unfortunately you'll probably be forced to offer what ever is standard in your area (even commensurate with similar non horsey jobs) to get good help.