Is this birthday gift too over the top for your best friend?

First of all my best friend is married and 30 years older than me. I know that's unusual for a twenty something year old to be that close to a 50 something year old but we are best friends. She's like a second Mom to me and her husband like a second father. We do everything together. I even go on family vacations and holidays with their family. Last Christmas I spent $500 on an exercise machine for her and her husband. It was a joint present that they have enjoyed throroughly this year. Her birthday is coming up in September and I've been thinking about it. We always make a big deal out of birthdays. I know that she's a business woman, but due to some recent hardships she's financially strapped. I was thinking of getting her an ipad and having it engraved. She's always checking her emails at work because she doesn't have a home computer and she loves her ipod and reading books. I figure this would be the perfect gift to tie all of it in together. I know she would love it, but I don't want to make her husband uncomfortable purchasing an expensive gift nor do I want her to feel bad that this would be the second present that I dropped at least $500 on for her. I have the money and I don't mind doing it, but still I don't want to make her feel bad. I know she said a couple of things about how much money I spent on Christmas and how she felt bad. Should I get her the ipad or look for something else less expensive? If I do get the ipad should I get it engraved and what should it say?