I do not think it is over the top. This make and break evening is actually a good idea. I like it. It is better than suddenly getting and email cutting it off.
But i recommend not doing anything you haven't done before unless it is something she would like to see.
Ask her what she expects out of the evening.
If you have never bought gold earrings before, then do not do it now.
Obviously you have provided flowers in the past, so this is ok.
Then think of something you know she likes in a relationship and try to serve that up.
Here is what I mean. She obviously believes something is missing, else she would not be considering breaking it off. So make part of your goal one of finding out what is missing; and then asking for a chance to show you can deliver.
I hesitate to provide humor suggestions, because humor is so personal. One person's joke is another person's insult. It can drop flat. Trying to use humor in the form of a joke may not work and might back fire. (see, I do not even like his humor).
Romantic, is something else. A simple candle will do, with dim lights and low music. If she likes Jazz, use soft jazz. Why not some Brazilian bosa nova jazz in the back ground. Of course she may not like jazz, so pick slow and smooth in her venue.
Approach the evening with humor and humility (where humor is an attitude).
One more thing about the flowers. Do not send them to work. No, send them to her home. And only send one or two of her favorite flower. Do not over do the number.
Then have a bouquet of her favorite flowers on the dinner table as part of the setting.
Do not put pressure on her. Make it a care free evening with a romantic atmosphere, where the doors to communication are open. Do not ask her why, oh why is this happening. focus on the pleasant evening.
Saver the heavy talk for a glass of truth serum (wine), sitting on the couch. Where you say, you know...I feel it would be a tragedy to let this relationship go by the wayside. then give her space to talk.
when she talks, maintain eye contact.
Be ready to say I understand. If she decides to move on, then leave the lines of communication open.