Anonymous wrote:OP, I get your concern. 5 years ago, I was a 38 year old overweight single woman who hadn't dated in nearly 8 years. I had a terrible breakup that I was pretty traumatized by, and then I struggled with depression for many of those years, then I was stuck doing elder care duties, and I just wasn't at all in a frame of mind to be dating.
I remember my brother once telling me how sad he was for me and how he really hoped I would get back out dating again, and that he really hoped I would get to be a mom. It did mean a lot to me that he validated my worth as a potential mother and potential partner, but I just wasn't in an emotional space to make those kinds of changes at the time.
FWIW, I'm 43 now and still just as overweight, but I'm married and have the most delightful, loving, wonderful 18 month old. I know I'm lucky; at 38 I had pretty much given up on conceiving my own child. I still struggle with depression, but I treat it as a chronic, treatable illness and work hard to take care of myself. I know I have a lot to offer the world as a mom and as a friend.
When I decided to put myself back out there, I really made it essentially like a job. I knew I would really need to make an effort. I actually had the most luck with Craigslist for dating -- I hated the "on the shelf waiting" feeling of Match and other dating services. With CL, I was in the driver's seat: I would post an ad in the W4M section saying I was looking for a companion for X activity (in public) for the weekend, something that I really enjoy, like biking or hiking or kayaking, etc. And then I would go meet the person for that activity. At worst, the dates were exercise with a weird person. At best, well, at best I met my now-husband.

Centering the meetup with the person around a fun activity really helped to normalize the pressure of meeting a stranger for a date, and it helped filter out people who had no shared interests with me. (Reading email replies helped, too, as I could filter out lots of people on punctuation and spelling alone.) But I knew I wasn't up for long correspondence, as I simply had no patience for it. My end goal was an in-person companion, so I kept the "online" part of online dating to a minimum, while focusing on the dating itself.
That's the long way 'round in saying that your sister really can't be prodded or poked into doing this. You can affirm how loveable and wonderful she is, but you can't make her do any of this. She has to want it enough for herself to actually do it. But I also shared my story to say that there's hope and she doesn't need to worry that she's too late. Even if she never marries, she could still have a child. And if she doesn't have a child, she could still be happy. But time is literally running out, in that our time here is completely finite, so if she is not living life fully now, I hope she will take steps to do so.