Is there a term for the blending of different recipies of the same type?

Fusion is a great word for a thorough mixing of things, conveying the idea of almost welding them together. So I see what your friend means when she describes your fusing together of different recipes for a particular dish as fusion cooking.

But when people use the term fusion in relation to cooking they often mean the marrying together of different types of cuisine, like for example, an "Asian Fusion" style restaurant might serve dishes from a variety of different countries within Asia or dishes made with ingredients from a variety of different parts of Asia ... like maybe curry with tofu in it or, who knows, sushi with paneer? They can be as creative as they like, and it's called "Fusion".

So if your friend were to write a review of your restaurant and call it a "fusion restaurant", she might need to add a little extra explanation to avoid con-fusion.

I don't know that there's really a name for it beyond "combining recipes" or more generally "modifying/changing/tweaking recipes." If your goal is to get the best of both worlds, then you could perhaps say you're trying to improve or perfect your recipe for something.

In the end, you're just making additional variations of an existing dish, presumably with the goal of finding a variation you really like. It's a really good method of doing so, and you should definitely be proud if you manage to succeed at getting what you want out of it! But you started out with raita recipes and you made another raita recipe.

If you were combining different dishes, from different cuisines in particular, resulting in a dish that couldn't exactly be described by just one original name, then fusion would be a good name, as Lorel said.