Contact colleges that have illustration courses, or animation. Maybe someone could pit a note on the board. Also, not sure if this is true but was once told if the illustrator's name is on the front cover then they expect half the profits - you may have to check this.
Perhaps an idea is to get a 'how to draw' how to illustrate' and maybe she could do it herself
I've been a children's book illustrator for 24 years.
I'm assuming you mean a private commission? Your not expecting it to be all printed and bound etc?
If you want a couple if small vignettes or pages illustrated then yes put an add up at a student college or online. If you want a full colour, all singing and dancing job then yes - it's too late for Christmas. It all depends on how good you want the work to be. An experienced professional illustrator won't be available (sorry, I never work in this way). A student may work for a flat fee, per page. They will own the copyright unless you draw up and contract to sign that officially buys them out.
Out of interest a mainstream publisher works nearly 2 years ahead of a Christmas publication. So people are already commissioning for 2019.
Could you post your job on peopleperhour website or similar and include the timescale of waning it before Xmas. You’ll get bids for the job and they’ll provide links / examples of their work. You aren’t obligated to accept any of the bids if you aren’t keen on any of them.
Is she hoping to have it published or is it more just for her own benefit?
Depending on the theme I would love to do it if it wasn’t very involved. I used to work in children’s book publishing and just draw a lot for fun and it doesn’t take me long. I wouldn’t have time for a fully illustrated picture book so it depends what the book is - if it’s an older reader’s book needing some line drawings I would gladly show you some to see if you liked them.