It definitely is different for everyone, but as someone who is ahem high quite often, there's a couple factors that play into it. First would be what she's high on. If it's weed, did she smoke, is it edibles, a dab pen, a joint? It'll be a bit different depending on what medium she's used. Also, how she's feeling before she smokes can have an affect. Being sad and high is NOT fun.
So for me, depending on how high I am, the main feeling I think would be relaxed. However, this also means I have no motivation to do anything, so unless I have a lot of inspiration to do an activity, I'll probably just lay in bed and eat and watch Netflix. You probably wouldn't want to make her full of energy when she's high, obviously, but, again, different products do different things. I would very much recommend research on whatever product she is using, and even what strand of weed if she's simply smoking blunts. But yeah, in short, hella relaxed, kind of woozy if I'm really up there. Like I don't fully know what's going on and time is either crawling or flying. Sometimes I disassociate and just daydream.
My biggest thing would be, don't over exaggerate it. Like yes, realistically when someone is really high, they will probably say "I'm so high," but with the experience I've had, it's so much more immersive and sounds better if you don't just straight out say things. Use adjectives like "fuzzy" or "woozy." Maybe she daydreams, maybe she gets really into her favorite tv series. There's room for different feelings, just try not to make it cliche.
I don't know if that helped, but let me know if you have any more specific questions, I'm happy to help!!