Pickle dilly!

Dear Miss L,
I get more good tips from your blog than anywhere! (thanks!! -LL) I have a small problem. My sister has this gigantic crush on my boyfriend. And we're no spring chickens! She's 30 and I'm 26. Every time my boyfriend comes around, she practically falls flat on her face, swooning around him. I get so mad and he thinks it's funny, but I've had enough. At any function where I have to see my sister (we are pretty close), she practically wets her pants if my boyfriend is within a hundred square miles. I'm not exaggerating! She calls him for stupid little things, and he's polite and tells me about it. I talked to her about it and she says she can't help it, that she would never do anything, blah blah.
Now I'm in a little pickle. In the beginning I wasn't that into my boyfriend, even fooling around a couple of times without him knowing. Now I feel like I am in love with him, and this crap comes up! I have anxiety attacks thinking he's going to find out about my fooling around (one time with a good friend of his), then just get mad and go and sleep with my damn sister for spite. (She's really attractive, and I think she may know about my past fooling around) I'm going a little nuts with this. Help me out here, Miss L.
Anonymously freaked

Hi Miss Freaked. Well, now you do seem to have a pickly situation. I would say you have every right to be anxious. Your little "affairs" may very well come back to bite you in the butt.
Let's get to understanding what's happening here. Your sister, even though she loves you, will always have a bit of sibling rivalry with you. Also, it's probably a great fantasy for her. She can also be in control of "tempting fate", which is empowering. It's much easier to find someone "close to home" than actually going out and doing the work and finding someone yourself. Explain all this to her, maybe she'll get the drift of why her pants are so wet. Then there's a couple of other things you might do.
First off, make sure the boyfriend is VERY happy with you, just for your own peace of mind. A guy (or a girl for that matter) won't just go bouncing off if they are happy and "satisfied". Also throw in a little "some other guy chasing me" things to get his natural posessiveness up a little. Tell your sister she needs to take a vacation from this "closeness" with you for a while. She's got to find someone she's more happy with than your guy, or this whole thing could blow up.
Keep your sister away from his friends. She's going to cause trouble there, too.
After some time this should all calm down. Even if he finds out about your "flings" and leaves for a bit, if he is in love with you, he'll be back. Men (and women) are like that. Hope you pull through, there, dilly girl. You cast a bad roll of the dice when you fooled around with someone he knew. That's a big no no. Always pick only one from the pack! :)