She's working 30 hours per week, which is what a lot of corporate employers do to avoid paying any benefits at all. So you are being very smart to pay her for her 2 weeks and holidays.
I think it's a slippery slope to argue about Good Friday vs. Buddhist holidays - you may not be aware of her religious traditions, or that of her husband or other family members. A lot of interfaith families have holiday obligations beyond the individual's own faith, so try to be open. If she has children who are off from school or a spouse who has the day off from work, she might have a legitimate reason for wanting time off. However, having been gone for a month until earlier this week should make her a little less demanding of time off. (On the other hand, if she's been gone, others may want her time on their day off, right?)
I'm surprised by the language barrier. If she is from India, she is very likely to be trilingual - English, Hindi and her regional language. Both English and Hindi are the official languages of India, regardless of region or religion.
If you do write up a contract, please have someone else check it for spelling and erroneous "autocorrect" changes - that really can mess people up anyway, and if you add in a language barrier, it's worse. I see that your computer or phone have made some changes in your post or allowed some incorrect spellings. It's not a problem for us, but if you are putting this into a contract, that's a big problem. You need a really good proofreader to help you above and beyond what your computer does automatically.
The other thing to consider would be a certain number of "floating" holidays. Maybe you want to give her the "bank holidays" since you are off anyway and maybe don't need her those days, but consider a few floating holidays that she can exchange for religious or random holidays of her own. So, for example, although Veterans Day is a bank holiday, if it's not important for you to have it off, maybe she can swap that for a day that works for her. It's a way for your to appear to be flexible and accommodating without taking an additional bite out of your budget.
I know that it's expensive for you, but remember that most companies give 10-15 days vacation, 5-10 sick days, 2 personal days, and 10 holidays. They also pay workers' compensation, Social Security (which you should be paying for her lest you go afoul of the law), 401(k), and profit sharing. It's part of the cost of doing business. I think if you keep track of the time you are already giving "here and there" and institute the use of a time sheet (you can find samples on line or at office supply stores like Staples), you will have really good records (and so will she).