I think its hard because although its a big sum of money, it could easily end up all spent on a home. We dont have a home of our own or a deposit, so if we won money a home of our own would be our top priority.
But this is maybe not the case for her if she's looking to have a bit of a spending spree.
After securing a home, I'd really want to pay back (and treat) my MIL and parents who have helped us out at various points in the past when we have been hard up and then a bit for siblings and very close friends - but I have a big family so it would really depend on the size of the win how much this would be. But certainly, I hope I'd treat them to smaller things that might mean a lot to them at the very least, just to share the luck and let them know I'm thinking of them.
You can either stay quiet and hope she finds her generous gene off her own back contrary to past behaviour, and resent her for spending it on other things.
Or you accept that she's a bit thoughtless, that she could be overlooking you not out of spite but because she's a bit self-centered, and may have always assumed you were comfortable financially and hint/say outright that she'll be able to pay you back now. Its probably what she would have done if you'd won money an hadn't (yet) treated her.
The timid, anxious part of me that hates making a fuss would probably have always done the former. But, I'm beginning to become more confident and this newer side of me would tend towards the latter because I'd feel that the other way sets her up to fail a secret test, from which you will infer means things about her relationship with you and I don't think that's fair.
Maybe she's not as thoughtful as you are, she's caught up in the excitement and may not have thought of treating you and that hurts. Of course it does. But you compound that if you silently resent her for something that she might have resolved if you had been open with her.