A slight quandary

It is nothing to be embarrassed about, I think you should have said, too late now.

Difficult!
I would say however, you are familiar with carpet moth (my sympathies!) but are you familiar with Persian rugs? Many old ones show signs of old damage, long dealt with.

If you don't know her well enough to guess at her reaction, then I think best to say nothing.
However, 2 possibilities:
Do you have a mutual friend that you could mention it to? Say you are happy (moth survivor) to have a word but didn't want to intrude, and see if friend can guide you.
Could you, on next meeting, have a conversation about Persian rugs? "they are so beautiful, but I don't know much about them..."

I have to say that unless a person (or sometimes an animal) is at risk, I tend towards saying nothing.

I’m a heart on my sleeve person and always say what I see, most often as it’s spontaneous I am not perceived as hurtful. I’m honest not anything else.

The specific type of damage caused by these little blighters is obvious to me. I had the opportunity to look at the rest of the rug and the rest was fine. I couldn't bring myself to say anything at the time somehow. I know. Its not like me to be polite!

I'm not sure; when you say evidence do you mean bare patches or did you see the little rice-like larvae?

If you saw any larvae perhaps you could have said "Ooh, I've had those in my rugs, carpet moths! they are such a nuisance. I found the best way to get rid of carpet moth is ****."

It was the characteristic white spots of canvas coming through plus little lines of chewed carpet. Im sure she'll have hoovered up before we came so would have removed the horrible white larvae and spent cases. (I know just too much about them!!)
I might be seeing her again this summer but she's very busy so can't count on it. I'll practise in advance how to somehow introduce the topic.

It's not just old, precious Persian rugs they like.

New wool carpets are targeted too. It's an ongoing battle with the vacuum cleaner nozzle and cedar/lavender spray! ☹

I know! We suffer. However, this lady has hardwood floors with rugs.

I think it would have been kind to mention it if you have some knowledge.. to help a lovely carpet!!

Rather slight, as you say.

Thanks for this post, it reminded me to check my stored carpet. A lot of hoovering has gone on and I can only hope I can keep the little beast at bay!

I’d tell her and perhaps give her advice on how to get rid of them. She would, most likely, be grateful. Good luck.

tell before it gets past it.