Point being - The judgement on whatever I do to my house, as part of a permitted development scheme, being considered 'in keeping' or not is nowt to do with a party wall agreement.
It's a negotiation though. Unless there's a requirement on her not to unreasonably withhold consent / agreement, then it's perfectly understandable that she might attempt to extract something in return for her agreement.
Whether this is a charitable, neighbourly action is another thing entirely.
Point being - The judgement on whatever I do to my house, as part of a permitted development scheme, being considered 'in keeping' or not is nowt to do with a party wall agreement.