Bra intervention for tween

[TattiePants]

I have a quick question for the bra experts. 11 year old DD has mainly been wearing M&S Angel bras for about a year in size 28B. I've just measured her and her cup size has gone up nearly an inch so went to buy some 28Cs but they don't do that size. Am I best ordering a 30B as a sister size?

Forget to add, she also wants a strapless bra. Would you stick with a 28B for that so it doesn't fall down!

If she has gone up to a C, you don’t necessarily need to stick to training bras. There are plenty of plain bras with no underwiring in the ladies section :)
as for strapless, you should really go for best fit to stop it either riding down or digging in. She’ll need to try them.

We looked in the women's first but with the exception of an Angel sports bra, they're all lacy. I might order more 28Bs in a different style and 30Bs then she can try them.