My son went to one at McDonalds once. It was free to have it in the play area. When the kids arrived, they bought a happy meal for just the kids invited to the party (parents and siblings bought their own) and the kids played on the playland after presents and cake. A happy meal is about $3-4, so for 10 kids, that'd be $30-40.
My niece had one at an indoor pool at the YMCA, and it was $60 for 1 1/2 hours in the pool and 1 hour in the party room. I just had my son's at Denton Natatorium, and the total was $110 for up to 12 kids, each additional kid was $2.50 (our ages were 6 & 7, the 5 year olds that came were only $1 each) more and that price included all the waters and capri suns we needed as well as plates / napkins / forks which would have easily been $50 or so if we'd have provided it. We ended up having 21 kids total and I only had to pay an extra $10. I think there is a natotium in the Hurst or Haltom City area, so maybe their deal is about the same.
Another thought, does she have any friends or family members with birthdays around the same time? You could go together and split the cost of some place.
Also, I agree with the previous poster. . . if you have the party at an off meal time, no one would expect a meal. Something like 2:00-4:00. You could get away with a bowl of pretzels (store brands are $1 a bag), maybe some veggies or fruit depending on what's on sale, some chips and hot sauce, etc. Some inexpensive meals. Or, if you want to feed them, we did a hot dog meal one time for my son's birthday and it was very cheap. There is a brand of hot dogs at walmart that are about 68 cents for an eight pack and the buns are $1. You just fed 8 people for less than $2! Much cheaper than pizza.