Okay. Here's the deal. IF there is something to disclose, then she must disclose it. However, if there's no problem (like, it's an old house and it has settled, but there are no structural problems), what is she supposed to disclose, exactly? Where does it end? Do you want her to disclose things like: the living room is painted blue, the bathroom sink has an unfashionable gold faucet... See where I'm going with this? You bought an older home. Older homes are not, and will never be, perfect. If you wanted to go after anyone, it would be your home inspector, but honestly if it's just routine settling of the home that was not noticeable with furniture in the room, you'd have a very hard time pinning even your inspector with that. It is really not that big of a deal. Let it go.
Now, if the sellers indicated they'd replace the siding and did not, go after that like a pit bull and don't let go. I would assume that you have signed documentation saying that they'd replace it? If so, it's as simple as the realtor arranging to have it fixed, and that amount is paid for out of escrow prior to the sellers receiving their money.
If the realtor failed to put any of that in writing, or did put in in writing but failed to have it taken care of, then yes, you probably do have a case against her. Hopefully you have e-mails, voicemails, something proving these repairs were discussed. Go to her broker first - brokers are required to carry Errors & Omissions insurance, and this would likely fall under that umbrella. Or, if you have a home warranty service, this is possibly even something that they would cover (read your policy).
Good luck.