Hi, A.. Well, the old wisdom teaches us that if a child walks early, she will talk late, and if she talks early, she will walk late. That's almost always the rule.
However, every baby develops at her own rate. It's clear that she isn't completely deaf or anything because she is aware of talking and is trying to talk, but she's just not getting out what we recognize as real words.
Toddlers at that age don't speak very clearly anyway, but your child might have some hearing loss...she's hearing people make sounds and words, but she night not be hearing them clearly, so she might be babbling the way she hears other people babble. Has she had a lot of ear infections? If so, she may have fluid buildup in her inner ears, and this keeps her from hearing clearly.
You don't need a speech therapist at this time; you need someone to try to figure out if she has a hearing problem. All kids learn to speak by hearing, and if they can't hear properly, they won't form real words.
It could be nothing at all, but your instincts could be quite right that something is wrong. Get a pediatrician to examine her ears, and get a referral if necessary to a pediatric specialist in hearing. It's hard to test a toddler's hearing, but they have ways to figure out if she's hearing properly or not.
I hope this is nothing, and that everything works out OK, but if she does have a problem, this is a good time to catch it and deal with it. The sooner, the better.
Peace,
Syl