Price impact when minting Dai-like stablecoin

[Hipshot]

Dai is just the best known example, but this applies to all decentralized algorithmic stablecoins that are backed by cryptocurrency as collateral. Anyone who owns accepted collateral (ETH, USDC etc) can open a MakerDao vault and generate more Dai. Newly minted Dai can then be used to buy more ETH or other collateral.

So, if Alice owns 1 million USDC, and also owns ETH that is worth >= 1.5 million USD, and want to spend 1 million dollar to buy ETH, there are 2 options: she can either buy directly spending the USDC (perhaps ETH will have a green 1-minute-candle because of it).

Or open a MakerDao maker vault, mint 1 million new Dai, and use these to buy ETH. (and again, perhaps ETH will have a green 1-minute-candle because of it)

Is the price impact on ETH in both cases the same? If yes, would someone who owns a very large (>50%) share of any coin that is accepted collateral be able to influence the price of that coin?