I have to agree that the email itself isn't that bad; it's the history behind the email. This person is having something done for her, and 1) you're not fond of her and 2) nobody did the same for you when you were laid up. So yeah, that's bound to cause some resentment. I'd definitely be annoyed too.
I used to work at this place and they did little things for people's birthdays. Nothing big, but they'd send around a card for people to sign, or they might get you a cupcake and some balloons. Just something to acknowledge you on your day. I'd been there several years when one year, I took off on my birthday. It was well known that I was taking the day of my birthday off (that is, people knew my birthday was coming up and what I was planning to do). Yet I never got a card or anything before I left. OK...fine. Maybe I'll get it when I get back. We had a company social outing (bowling) that weekend and I thought, 'oh, I bet they're going to surprise me with something during the outing!' Yet nothing ever happened. I was soooooo let down....my coworkers had forgotten my birthday. Other people took their birthdays off and still got the card/acknowledgement. Yet I got nothing that year, not even the words "Happy Birthday" from a single one of them. And let me tell you, when Annoying, Suck-Up coworker's birthday rolled around a few months later and they sent around the card for everyone to sign and made the usual semi-big deal about it, it really rubbed me the wrong way. I think I signed the card b/c it would have stood out if I didn't, but I certainly didn't do anything else. The inequality of seeing it done for someone else but not for me really hurt. yet you can't say anything without sounding petty and like you're whining.
So yeah, don't even respond. If by chance they actually seek you out and pressure you, that's when you can treat them to the incredulous look followed by the "No, thank you" response, or if you're really brave, "Why would I want to do that?" or "I'm pretty busy right now, and besides, I managed just fine on my own after my surgery. I think with her husband home for the week, they'll do just fine without my help."