Thicker formula harder for baby to drink

My 2 month old was having horrible acid reflux so her dr wanted us to get her on a thicker formula to help keep it down, which it has been. She’s barely been spitting up or coughing at all which is great.

But since it’s so thick, almost like smoothie consistency, it’s very hard for her to drink. She’s a premie so she’s had issues taking a bottle from the start, but now this has set her back a lot because her suck isn’t the strongest as is and it’s so thick to come through the nipple.

Her drs wanted her one a 1 size nipple because she gets ahead of herself and will choke while eating or forget to breath.

She’s only taking barely 15-20ml every feed now (we have to g tube the rest after 20 mins). Should I try her at a 2 size nipple and see if that helps? I don’t want to push her too much, but it set her back so far. She was doing so great with her previous formula with how much she was able to take.