What was the best present you had leading up to the birth of your baby? My sister-in-law is about to give birth to her second and is dreading it as her first experience wasn't too good. Like to get her something she would really appreciate.
I would personally do a gift basket for her.. stuff she really loves.. favourite chocs, sweets, lotions, smellies, all things that make her smile and she can indulger herself with :)
Could you be with her when she gives birth? That is the best gift you could give as all the studies into childbirth say that to have a trusted female friend or relative with you gives you a much better chance of things going well. This is as well as the partner not instead of. If the staff object point them in the direction of the research, there's plenty of it and most good Midwives should know about it.
If you can afford to, how about paying for a maternity nurse for a few nights after she comes home from hospital? Especially if she had a bad experience the first time could give her some sleep and help the new arrival into a routine.