It’ll probably take some time for her to get over the embarrassment or awkwardness talking about sexual things, especially if it’s deeply engrained… If sex positions are the one thing she’s comfortable speaking up about, maybe focus on trying out different sex positions. Maybe she’ll start to communicate a little more about what kinds of positions she likes and doesn’t like. My two favorite positions are ones we only recently tried for the first time in the past couple months. Since each position is a bit different, you can experiment to see what angles she likes, hard or gentle, fast or slow, etc 
This is a collection of sex positions you could browse to find some new ones to try 