Thank you for your question!
Reading is receptive. That is, the child is 'receiving' rather than producing. Therefore, your daughter can read words (that are produced for her) more easily than she can spell. (Spelling requires her to 'produce', whereas reading only requires her to receive).
Generally 'receptive' understanding and skills precede 'productive' skills by about two years. Therefore, it would be best to begin with a spelling program that is at least two years below her reading level.
I would suggest, so she has success, that you begin with My Very First Catholic Speller. However, it is crucial that she start at the beginning and is provided a strong foundation in this subject so that she can succeed. Spelling will only become more complex and difficult as she progresses through the higher grades. Also, if you start with the easiest level and work up, this will perhaps help her become more confident and less frustrated. It is important that she feel successful in something that is difficult for her.
As far as word and sound grouping, a-signal-e is the first 'AY' sound introduced in My Very First Catholic Speller. However, as with most good phonics-based programs, the My Catholic Speller series does then begin to group words that contain the long 'A' sound, with different vowel/consonant combinations. The reason that phonics-based programs follow this system is due to the simple fact that they share the common sound; thus it is logical to group the words together.
Consistent practice and drilling will also help your daughter learn the spelling words.
Here are some other activities that you could use, besides the drilling, that might help keep the interest level. For instance, you could buy her different colored gel pens, so that she could write her words in different colors. One favorite activity with my students was buying alphabet letters made of foam. The students then spelled their words for the week, using the letters. You don't, of course, have to buy the foam letters. You could simply write the letters on index cards, and use those to spell words. Another idea might be to pick a word for every day, from her spelling list. Your daughter could spell the word aloud, write it down on a card to put on the wall, write the definition and then use it in a sentence, or two. The more that she interacts and works with the words, the more likely she is to remember them.
Another activity I would highly encourage is for her to read as much as possible. The more your daughter reads, the wider her vocabulary will become. Also, the more she sees the words used in context, the more she will remember how they are spelled.
God bless you and your family and a blessed new year!