Hi @petalique, I've been crocheting for about 50 years so I have some experience here :-)
For a light worsted weight yarn I would use a size 7 or even an H/8. A size 5 would be better if you were making something you wanted to be fairly tightly crocheted, such as a soft toy you intended to stuff so wanted no spaces for the stuffing to leak out. In Australia yarn labels generally come with a recommended needle size- do yours?

Petalique, hooks are so inexpensive, I'd send her a variety of hook sizes for her to play with. Typically the yarn manufacturers will list the size hook that will work best with the yarn to produce the given gauge. But everyone is different in how they tension the yarn so can get different results.

The important thing is the hook should be able to fit the yarn to pull the whole yarn and not split threads. If you have a small hook with a chunky yarn, it's clearly not going to work. A too large hook can be used purposely to yield a softer, more open and airier product, but not the other way around.

Also the size of hooks, be they numbers or letters, are being replaced with mm sizes as they are more consistent across countries. Here is a table that shows the recommended hook size for the size of the yarn:

Also, while it's individual, I find that I prefer, and others I've talked to prefer a more pointy head ... here they call it "inline" on the hook rather than a rounded one...I find it easier to pierce the fabric while you're working on it.

Another consideration would be for your friend's vision. As I've gotten older, it's harder to see smaller stuff, so I prefer the larger size hooks vs. the smaller ones. When I've taught, I usually request the students bring worsted weight acrylic yarn and an I or J (5.5 - 6 mm) hook as it's easier to see the stitches if they are a bit larger.

Below is a chart that does the hook size conversions.

I'm a longtime crocheter as well (62 yrs). I can give an opinion, but there's more to consider than an opinion alone. Annie’s info is very helpful. My mother most often used an F hook with worsted weight because she crocheted loosely. I most often use a G hook s as my stitches were a bit tighter than Mom’s. Mom preferred hooks that had a tapered tip. With my tighter stitches, I prefer the inline tips (no struggle to find my spot) and I can crochet faster. The tapered hook stands away from the hole and sometimes I get caught on the way out of the stitch.

And I’ve found that worsted weight isn’t all the same thickness, depending on content.

Unless you know her crocheting “groove”, you might be better off with a small selection of hooks.

I've looked at the Joann's website - they sell that particular yarn- and they recommend a size 8/H.

Thank you all so much. DH helped me by picking up some hooks (set). I have not yet taken a look, but I hope they are the inline type as Annie likes and suggested. She just turned 80 and were bifocals. I have not seen the acryllic yarn and it was all on sale, so probably not returnable. She will have fun with it and we can always get another type.

I have a sizable stash of wool, alpaca-wool, and mohair/wool yarn but I think it is maybe a bit too dear for her to practice - play with. Not sure that I will use it. I rarely wear sweaters and DH doesn’t either. I don’t think I ever wear the hand knits I made.

I also have lots of patterns, books and so on. I have to do some serious dinging.

If you get the yarn from Jo-Anns, so long as they are full skeins, they are returnable.

As far as acrylic yarns, I like red heart the least. I like Lion Brand. I don 't have enough experience with Big Twist to have a solid opinion.

I also agree with Donna that the labeled weight of the yarn is only a suggestion...I've seen some much thinner or thicker yarns that are all labeled worsted weight...even among the same manufacturer.

If you're planning to discard yard and/or patterns, please consider having a look on Ravelry for groups that knit for charities. I belong to one and we're always thrilled to receive donations of yarn and patterns. We have a lot of ladies who love to knit but can't afford yarn, so we pass donated yarn on to them. (Please note, I'm not suggesting you send it to my group as we're in Australia.) Keeps stuff out of landfill and helps clothe someone in need.

In our town, the senior center will take yarns and other craft items. Also will some libraries that run knitting groups and such.

Thanks for your suggestions.

Looks like the cr hooks dh got are the tapered ones.

They look like they want to have little eyes and mouths.

I may need to borrow one to fix a very long pulled yarn in a Bombas woolen sock.

Is it difficult to find the ”inline” hooks?

No, I usually get Susan Bates. Joanns carries them.