Dear Pixies Ladies

Can you advise - I'd like to buy a vibrator for our fun. What should I go for. I know I should ask but I'd like it to be a surprise.

My partner loves penetration and I have always wanted to use my tongue whilst she enjoys being filled up.

Does the size matter or is it the features? Should I get one bigger than mine for the novelty, I'm 8 x 6 - but I'm a little concerned with thrush and cystitis, which is a problem we have.

All advice and recommendations welcomed.