I do a lot of hw with ss14. You can test how much she's learning and gauge your method by making up some problems of your own when you have her and watching her solve it on her own. You can word it how you want. Does she substantially know what to do? Or is she helplessly waiting for you to do it for her?

The process usually goes in reverse for me because SS is autistic. I let him tackle the hw then I start breaking it down to simpler steps when I see he can't get it.

I think it's nice she turns to you on this one topic. It's a nice little relationship builder. But I agree you should be careful that she is not just using you as a free math service. Make sure she's really learning it. Make the "test" exercises on your time fun. Don't let her know she's being "tested." Just say you want to go over it with her. You can even tell her you need HER help! Whatever, I would definitely nurture this little thing you have going and nurture her at the same time.

I don't help SD11 at all usually.
She'll go to DP most of the time if he is in the mood.
She has asked for assistance with a tricky word problem here or there which I am better at than DP (and that's saying a lot since those things had me in tears as a kid). But I sit and make sure SHE does the work, I just help her break the question into logical pieces.

SD9 rarely asks for help and mostly does her work on her own.
If she lets it known that she has a reading comprehension section, not her strong suit, sometimes I'll sit down and go over it with her - DP for some reason disagrees with homework at all and will avoid it - but I suspect most of the time she just wants to talk it out. If she complains about being bored...well, is your homework done?...usually solves that issue.

The good thing is this year in middle school SD11 doesn't have too much homework; most work is done in class or in homeroom in the mornings.
SD9 has a really good teacher who assigns very short homework, usually relating to what they worked directly on that week in class.
So it's been a good year so far.

No way would I do it over the phone.

When OSD was younger I only helped when they asked. When they did I had to make sure they attempted the problem first instead of asking me to walk them through each one step by step, because with three kids we would never have gotten through a night of homework...

I would ask your SD to send you a picture message of what she is stuck on (the work she has done so far) that way you can better guide her and you dont feel like you are doing the work for her.

I help with homework all the time. Some weekends SS and I have done over 20 missing assignments together. It's exhausting.

If he asks me for help the first thing I say is, did you read the instructions. Answer is usually No. After that, if he still can't get it, I sit down and show him how to get the answer on his own. It's only 4th grade, so all the answers are in the book. He just has to learn how to look in the right places.

He usually always tells me he had fun. Which I find ironic. He does zero homework at BM's but she swears she does it with him every night. I call BS. He loves the one-on-one attention and does the work with me without argument.