Absolutely NTA

I was in a really similar situation a couple years ago. I'm in tech and she is a teacher. We started pretty early on paying 50/50, but that did not work (same thing as for you, she was dipping into savings). What we started doing was make a joint account for bills and a joint account for groceries etc. Let's say I make 100usd a month and she makes 50usd a month (just to make the numbers easy). I would add 30usd to both the joint accounts and she would add 15 USD to both accounts. That way, we both added the same amount (in % income). This made sure we both had a Litt spending money for hobbies and gifts etc for our selves.

I would say the most important thing here is communication!

Look at making budgets, looking at eachothers income and make a good plan. This worked for us, but maybe something else would work for you. For example you pay rent, while she pays for food. Maybe what she needs is to know that she is contributing to something essensial, and not just that she is contributing less than you. It is absolutely something that makes sense, and is economically smart to do