HIPP AR nipple size - plz help!!

I’ve seen a few threads on this but not sure it fits my experience. I just switched to HiPP AR for my two month old. Size 1 and size 2 dr brown don’t seem to let the formula through due to thickness. Size Y does - but I’m worried it’s too quick even though she’s not having a problem with it, but the label says 9+ months and she’s only 2! Can someone help share their experience please!