We have been advised to go for a mini-mal but have been advised 2 lengths. 1 surf shop said 7ft max and another said 7'6

We have a maximum budget of £300 all in so leash, bag etc.... have to come in with that.
She will be surfing approx 3 times a week summer and once a week when school restarts.
She is very tall for her age 5'3 and a bit lol. And she weighs approx 6 stone (slightly under that is anything)
We want a good board that will last her a long time and take a lot of dings etc.. Also would like to keep this board as we get a lot of flat days in bournemouth, so at least she can take it out still and have a fun day on it.
Any help very gratefully received, as i am totally new to all this surf stuff and my brain is getting friend with all the different info