A few tips that I’ve seen here:
Put a piece of slate in the enclosure and use it for serving food. The tortoise will hit it with her beak while eating and naturally wear it down.
Use a pair of fingernail clippers and trim it yourself. A little bit at a time.
Find an experienced vet to do it.
Your tort’s beak doesn’t look too bad. The slate may do the trick. Also using cuttle bone sold for birds also helps keep it trimmed.