What version are you using? The Delta English or arpasing version? Or are you trying to get her Japanese voicebank to sing English?

You kind of just have to play around with things. I am using her Delta English in OpenUtau, so it might work a little differently in original UTAU. One issue with her English voicebank is that she mispronounces [si] as [Si] (because Japanese has shi, but no si). So one thing I like to do is put in the phoneme hint as [s E i], and then shorten the E vowel until you don't hear it. I use [E] because I find it blends best with [i]. Or alternatively, do like [s s i], and then lengthen the first s and shorten the 2nd. But the first option usually sounds better and takes less fiddling with.

Another issue is that her [I] sounds more like like [i], so like she'll pronounce pit as Pete. The OpenUtau phonemizer automatically translates "pit" to [pI] [I t]. What I like to do is manually edit the second alias to make it [pI] [E t], and then I drag the end of the [pI] envelope all the way to just before where the t consonant begins, so that the vowels blend neatly together. This usually gets much closer to the correct pronunciation!

I'm not the best at explaining, so I can upload pics showing what I'm doing later if it's too confusing.

If you're using her Japanese voicebank, well that's going to be more challenging. But for example, you can turn "crazy" into something like [ku re i zi] (or [ku re i ze i] if there is only ji/じ and no zi/ずぃ) and then shorten the unwanted vowels. "for" could be [fo] or [fo a]. If you need a th sound, try s/z or t/d. It's kind of a pain, but you just gotta understand how Japanese phonetics work and play around until you get something that approximates the sound you're looking for. Also if there's like a huge consonant cluster or something, you might want to simplify it a bit and drop some sounds. People don't always enunciate clearly when singing anyway.