Make sure she knows to over-invite as not everyone will be able to come. Expect about 1/3 of the number of people invited. So to get 8 people to attend, invite about 25.
Encourage friends to bring a friend - the more the merrier!
Highlight the hostess benefits and ask her what she'd like to earn (maybe she has her eye on the Big Shot at 1/2 price) and then set a plan to work towards. ($400 in sales means about 10-12 average orders).
Be sure to show the catalog to those who cannot attend and ask if they'd like to place an order.
If you offer an incentive for outside orders be sure to highlight that to her in advance of her workshop.
Do not stress on cooking and cleaning. Just straighten up and provide simple snack!