You have a couple of issues here:
1.
Cost of online education. The first thing I would do is check to see if you county or state has online charter high schools as an option. Some states do and others do not. This would be free. Failing that, I would take a look at some of the cheaper online schools on this site like
Penn Foster High School. The entire program is about $1300, I believe, and they accept payments. There are other choices. Take a look.
2.
Overall ability to be successful with an online high school. This is a difficult one because she has struggled elsewhere perhaps due to ADHD and other issues. Typically, online high schooling requires more dedication and not less. Whether she could be successful needs to be evaluated carefully.
Questions?
Tom Nixon