While I do agree with the views of PP's about giving Suzy a listening ear, I do have one counterpoint.
There may be some information that you may share about your upcoming wedding with Suzy that could help validate her feelings of frustration with Veronica. And if you validate her feelings, that might strengthen her spine when it comes to dealing with any possible lack of reasonableness on Veronica's part.
Suzy: "Ugh! Veronica wants me and the other broke MOH to host her wedding shower for 70 people at Chez $$$! I can't believe I'm not able to enjoy being an MOH."
LadyL: "Wow. Host 70 people there? Just wow."
Suzy: "I don't know how I'm going to tell her I can't do it."
LadyL: "I'd suggest as quickly as possible. Would you like to know what was done for my shower? I really enjoyed it and it might give you and Co-MOH some ideas." LadyL could even share a variation of 'I'm afraid that won't be possible' such as 'I'm afraid that won't be possible to do x, but here's what we can do. It's y. What do you think?'
Throughout the hypothetical conversation, Suzy may be fortified by comparing Veronica with how LadyL is doing things. This would be very helpful to to Suzy as she navigates any Bridezilla tendencies in Veronica.
Also, for me, it's difficult to listen to someone complain about a situation, repeatedly, and not make positive effort towards fixing it. It'd be one thing if Suzy was a strong person that came into the office and said with affectionate exasperation, "Guess what Veronica is up to now...(blah, blah, blah - insert outrageous antic here) but I let her know, 'Sorry Zilla, you can't do that'!" They share a chuckle and move on.
But LadyL, eventually, this will all pass and it will be business as usual. Best wishes!