Can you not just

her? She sounds like a right cantankerous biddy! lol
Serious now... if youve decided what you want then stick to it! Tell her you're more than willing to split the cost of that, but anything above and beyond it is her responsibility!
The couple who are getting married before us rang and asked if we wanted to split the cost of the flowers. We had already decided we werent going to have any in the church, but she made me feel so guilty! But i stuck to my guns (maybe she'll leave hers there anyway! lol)
Love Dawn xxx
