It's honestly just practice. Although you two might be more comfortable discussing in English, try to make an effort to only use Spanish with her as much as possible. There will be a period of discomfort, but over time you'll become more and more at ease with regular use. Maybe try to set a rule where you only speak Spanish at home unless there's an emergency or something along those lines?

Hola Jermaine, espero estés bien. I agree with what Ryan says. I had a German student who was married to a Mexican and I recommended him to ask her for help to tag objects at home to learn basic vocabulary. You can also tag pictures to learn words related to family members, IKEA's and all sorts of catalogs or flyers to keep your vocabulary growing. I also recommend watching TV programs without English subtitles or with the Spanish ones activated to sharp your listening skills. Of course, once you've done that it's crucial to start using these words in complete sentences. Even if she's not a professional teacher, as a native speaker she can correct your grammar mistakes and improve your pronunciation . You are soo lucky to have a relative who's a native. Take advantage of it. ¡Buena suerte!

Just tell her to talk to you in Spanish only. After a while you'll be forced to learn the language 😁