If she were mine, I would retire her rather than breeding her again. Udder suspension is a genetic trait. In dairy cattle, there are pretty good records to use in selecting a sire to improve that trait but I don't think such records are much available in goats.
I sympathize.
In case it can help anyone: For the mastitis, do you strip (meaning hand milk a few streams) onto something that lets you see if there are any clumps in the milk? That would at least let you treat it as soon as possible. Sending a sample in to see which type it is will also help with treatment and decisions. It is best to milk the affected goats last, especially when the mastitis is active but all the time can help manage it.