This will come across as a little crass, but just being honest. In the bowl, the SD (or a SM) is a buyer. We know what we want, what we may consider and want we don’t want. If you want a 20-24 year old thin blonde with a large chest you may consider a 25 year old thin brunette with a large chest, but you will not consider a 33 year old average blond with an average chest.
Something to consider #1: In the next two months she could lose the extra 20 lbs or a fair portion of it. If you blow her off now, she’ll likely not reply to you later when you really want her because she’s your 10. So, be open and honest with her. Maybe she’ll ask you to help with her exercises!?!
Something to consider #2: Where is the extra 20 lbs? If it’s all in the butt – it’s going to stay. If it’s in the stomach, it will likely take longer to go away – patience is needed but if successful patience could be rewarded. If it’s evenly spread over her whole body so that she’s still proportional – is it a problem? If it’s all in her chest – is it a problem?
If you really want to see her if she loses the extra 20 or are willing to meet time to time if she mentions she’s working to drop the extra weight, would suggest saying something like: “…the vibe just did not feel right. Maybe in a week we can try again? Maybe it was just nervousness or …” This way if she drops the weight you’re still there ahead of anyone else.
Once you ghost or otherwise piss her off, if she remembers you the chance of meeting her if she becomes your 10 are likely 0% unless you go WAY over budget. Worse she could play you to make you waste your time.