If you want to dry her off - yes put her on only hay and water until she is dry, and then only maintenance ration (mine will get a handfull of goat mix and some sokaed sugarbeet shreds for that, maybe a few oats).
if you want to continue milking her, maintain feed (which is what?) and milk her twice a day. Completely remove the kid (behind a fence/hurdle). I found that my older girl (who had suckled her first kid when she came to me with her) is very canny and can put herself into a position where the kid can get her mouth through the bars and suckle... they are bright animals and her first duty is to her baby afterall...
If you think she is not quite in good condition (and you aren't desperate for the milk) - dry her off and then once she is dry give her a slightly higher ration - but make sure she is staying trim. If you plan to put her into kid (did she have triplets this year - if yes, don't) this autumn, make sure she is not going fat. I have had both my GG's down with Pregnancy toxeamia a couple of years ago - very stressful. This last year I made sure that the in-kid girl was quite slim, and only increased her food to more than maintenance in the last 6 weeks. She ate (albeit with strange preferences) till the end and delivered triplets with no problems! Now as skinny as a rake, but milking fine (and eating

) well enough.
But I also found that my T who had quite a few lumps in her udder all summer - all of a sudden they were gone in autumn. I can't even remember when exactly...., so if she is well (and more importantly doesn't get any worse - as in hot udder, runs a temperature etc) just keep doing what you are doing.
For what it's worth I also did the following: when I suspected another case of subclinical mastitis in my BT in the autumn I found an article that recommended feeding the goats quite high quantities of dolomite (a mineral containing Ca and Mg) - I increased the amounts of Caprivite - and vitamin C (powder available from health food shops as an ingredient in bread making, it is made by Doves Farms). It didn't increase the milk yields to really high levels but they recovered to what I would expect in late summer/autumn. Her udder is now soft and she is still being milked (run through). She did get to 1560kgs in her 365 day period.
There is a book: "Natural goat care" by Pat Coleby. Very interesting, if not relevant in all places as it is written for Australia and US.