I think she just saying it, but not quite meant what she is saying. They knew all along that they want and will get married, his mom really love Chompoo she even go to Chompoo lakorn set to take care of her when Chom isn't feeling too well. Reason they waited this long is because of her dad was sick for so long, and she want to take care of her dad first. And when her dad pass away, it wasn't right to get married right away, that's why the wedding was now instead of earlier. Also yes Nott got lots of money, and can give Chompoo anything she want, but Chompoo is making a lot on her own too, and she has always been high maintenance or spurge on things. Saw her interview once, she said she does spend money on herself, but only what she can afford, if she know she can't afford and don't have money she will never spend like crazy. She also does gives to charity too. With Nott's family being a high society family, and his mom is crazy about Chompoo, I'm sure his mom has a hand in all these extravaganza wedding as well.
Look at Don's mom she went crazy with Don's wedding too, so I can picture Nott's mom being just as crazy with this wedding as much as Chompoo.