Sidelined
I'm probably destined to keep answering as I can't be hurtful. I don't quite know why she bothers with me as I've not got much to offer. Perhaps she thinks, as my life must be so boring in comparison, she's doing me a favour?
If the mails are almost daily - goodness, where does she find the time! - then you're in a spot if you don't want to offend or be hurtful.
Perhaps the kindest way to deal with it without hurting her feelings is to simply say that you are for the moment quite busy and may not be able to respond to her mails in a timely manner. That way, she might just back off a bit.
Everyone has busy periods in their lives - you don't need to go into detail about it - just make sure she doesn't feel ignored but that you don't feel compelled to keep answering. You could even miss out a couple of responses, apologise, wish her well, congratulate her on her "successes", and just let it all dwindle.
When I write long emails to friends (which isn't that often) I always add that the recipient shouldn't feel compelled to answer in any great detail - and more importantly, at their leisure. I assume that, like me, they have quite a lot of 'life admin' going on, and what with text messages, WhatsApp, emails, 'phone calls, etc - all of which can be quite time-consuming - they won't necessarily have time to reply any time soon - or even at all.
Emojis are quite useful, too. An acknowledgement without the necessity for a written response?