Definitely take your daughter with you when you buy it.

Don't think about it lasting through more than one season if your daughter is growing like a 13 year old. There will be someone that needs that size next year or the year after that will help support your next purchase.

As for the fit. If she wears a glove, have it handy, put her hand in different size gloves, both first-base gloves and catcher's mitts. Start with really big ones and move down based on how she is able to squeeze the ball. The better she manipulates the glove in the store, the better it fits her hand right now.

The reason I write: try first-base gloves is because my catcher this summer has both. She ended up having more access to the ball with the 1B mitt. She suffered a bout with catcher's thumb and with research her mom and dad figured out that with the catchers mitt, the padding was there,but room for the ball was not...so she was not catching the ball just right. The 1B mitt allowed her to snag more wild pitches and her passed ball % went down. She still had the padding she needed to protect the hand and thumb.

Also get a new glove long before the season starts so she has time to break it in properly.

Hoep it helps!