First of all, you don't know for certain what she owns. Refusing to answer someone's pointed and possibly prickly question is hardly "proof" that she's renting Interval weeks. Secondly, VSE non-owners would be hard pressed to get a Christmas week in Hawaii or a platinum ski week using SOs, let alone Interval. I tried to use SOs to book a ski week in late Feb/early March using SOs a few years ago and was unable to. First exchange where I got a goose egg. I highly doubt any of these weeks would EVER be deposited in Interval.
FYI, for many VSE resorts, Xmas/New Year's weeks are considered "event weeks" that SO exchangers aren't able to exchange into them, even if an owner happened to exchange their event week for a non-event week. So the fact that you're not able to get in to an event week as an exchanger is evidence of nothing nefarious. In fact, it's more likely that she is, in fact, an owner.
Like it or not, VSE availability is tightening up quite a bit. And that is frustrating. But unless I had 100% proof that someone was obviously breaking the rules, I'd resist the temptation to "turn them in." Do unto others and all that.
I recently saw a lot of prime weeks listed on eBay at a resort that I am very familiar with and it's impossible availability during this time frame. I believed they were most likely exchanges. I contacted the person listing the weeks. I am now of the belief that these are owner weeks. As stated, if these valuable weeks were indeed exchanges, then this person was extremely lucky to have snagged that many fantastic exchanges.
To the OP, for sake of argument; how do you know that if the person hadn't snagged the so-called exchange, that you would have been the next lucky one to have gotten it? Yes, it is frustrating when you believe that someone is doing something that is taking away from others. However, be absolutely sure you know for sure. If this person is indeed renting all these valuable weeks and they are exchanges, then II will eventually put an end to it. A pattern will have been formed. Interval could rent those deposits out possibly to their benefit. I don't think Interval would want potential rentals (to put money in their own pocket) to go to someone that is breaking their established rules.
I would recommend that you either rent from the lady or move on. A few years ago I called someone out on TUG (new guest) that was listing units that I was seeing last minute in RCI. I questioned the person and these were clearly exchanges. Not ownership; guest certificate required. Apparently I handled it badly by posting and not private messaging the moderators. I was informed that there are volume renters that get inventory from RCI to rent out. I had never heard of such a thing previously on TUG. I was called out by the new guest and at least a couple of other Tuggers and was admonished for my posting. The mantra has always been that if a guest certificate is required from one of the two major exchange companies that they are indeed exchanges.
Apparently, that is not always the case. The woman may be evasive, as previously stated, for other reasons. Are you going to rent her week and are you serious about the transaction? She doesn't have to provide you with every last detail about her rental at this point. I rent my weeks and I probably give out more information than I should to "potential" renters, who are actually just tire-kicking and have no intentions of renting.
IMHO, think before reacting. All may not be as it seems. If you need the week, rent it. If it's that prime, it's not coming up as an exchange.