Your kid is at an age where her language skills are slowly and steadily getting honed. At 5+, every child is in an exploration mode, and exploring different languages is definitely on the cards. Language in itself is beautiful, and so getting attracted to various forms of it is quite natural. Whether your child is interested in a particular language or you want to make her learn something, either way the best step forwards is to start building vocabulary.
What you need to know
It is not possible to dump a barrage of vocabulary on a 5 year old, so the best way is to teach one word each day. Start with simple day-to-to-day words that are easy to understand and remember. Make it a ritual to learn a new word everyday and bring it into conversation on following days. This way, in a playful way your child will keep learning, and no time she will have a substantial stock of vocabulary that she can use in his/her daily conversations.
If you want to go a little further, you can also introduce a word and give the versions of the word in other languages that she might need in the future. But don't rush. It is important to gauge how much the kid is able to grasp and understand. At every stage you have to ensure that you child is not burdened and the learning process is smooth and seamless. One word each day will be a success only when the first word you teach yourself is patience!