How much of these things that you do together does she initiate? Does she go along with things you suggest or is she the one suggesting you do things together? If you are the one always suggesting and she is the one that goes along with it, I think you should let her ask. When you are swimming together, does she ask, "are we swimming tomorrow?"
I know a guy that has been waiting in the "just friends" wings for years now waiting for this girl to take notice. What he didn't seem to realize is that she never had any romantic interest in him, but he just kept holding on (I know this because she told me). He was a great guy, always helping her out and being really supportive of her, but it wasn't happening. I don't want you to find out that you are one of those guys that is being used for companionship only. For all you know, she thinks all you want is friendship too.
This advice might not go over that great, but my thinking is that you need to ask and take the guess work out of it. When you do that is up to you, but you deserve to have a feel for where you stand.
Frank you also won't like this advice I think because you are worried she'll move on if you aren't hovering around (which incidentally was this other guys problem). I think you should back away for a couple weeks and see how it goes. She needs a little Frank-free time to work through this stuff...that means no swimming, no racquetball, no favors, no lunch, no making calls to her. Just get the kids, meet your step-son, but don't do much about her. If she wonders why you are being standoffish then I guess you'll know that she missed your company.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
