How to handle the teenage girls??

When kids gets older, a benefit is that they have a say in things, and this can make parent's job easier. Your DD, at 10 yrs, is old enough to have an opinion about this. Check with her how she feels how about you talking to the girls or their mothers about this, and take your cues from what she says.

My personal opinion is do not talk to the girls or the mothers yet. Such teasing and dealing with it is part of growing up. If these girls stop teasing, some other teasing might happen some time in the future. Better to help your child learn how to handle it.

I would suggest talking with your child about it. In a relaxed place, at a time when you are not rushed, and it is just the two of you. The key is to not make it your problem.It is not your job to make sure her environment and friends are totally free of teasing and other life's little unpleasantnesses. So, discuss it, brainstorm with her - let her describe what is happening, why, and what are the possible solutions. Just prompt now and then with gentle questions like:
'why do you think those girls tease you',
'except for teasing, are they otherwise ok to play with'
'you cannot control their actions.... what are ways in which u could react/respond'

There are some standard ways for kids to deal with teasing/bullying (ignore, distract, agree with the teaser, pithy comeback retort, leave, divide & conquer, make friends with *one* from the teasing crowd, respond with same phrase over and over, blank look...) . Google it, one such article is this one: Teach Your Child to Deal with Teasing
Note down some strategies from that and other web sites, and during the discussion with DD, try to give her hints/clues so she comes up with those strategies herself.

You could try role-playing with her... you be the teaser and she responds using the different strategies she's come up with. Then, switch, and she teases you and you enact how to respond.

The key in discussions with DD is to keep it light and casual. Don't give the teasing more importance than it deserves. My guess is that if she is able to discuss it with you once in a while, she'll figure out how to handle it herself.

One more thing to do would be to talk to the girls' mothers - but tactfully. Pick one mother who is the most reasonable or you know fairly well, or pick the mother of a kid who is your Dd's closest friend. When you happen to meet that mom, tell her casually about what is going on. Present it like you are asking her for suggestions "one mom to another". Do not blame her child or the other girls, simply present the situation and ask for suggestions. Do not do this over phone or email...

Even if she doesn't have suggestions, she at least knows what is going on, might talk to her child about it, and above all, she is not upset that you blamed her child. No parent likes to be told their child did anything wrong.

Good Luck. Generally, these things pass with time too. Children change friends for no reason or for big reasons... and the teasing/bullying or 'no one plays with me' is often harder on the parent than the child.