There were quite a few marriages for political purposes at that age, but they usually weren't consummated.
Contrary to what people now think, medieval people weren't idiots. They were aware that the younger a woman was, the less likely she was to survive childbirth - and since the entire purpose of a medieval noblewoman revolved around giving her husband children and providing alliances, an early death or infertility made her useless.
For example, a temporary peace was brokered during the Hundred Years War which included the marriage of Richard II to the French princess Isabella. She was 7 at the time of their marriage; Richard was 29 and a widower. Their marriage was never consummated - they developed a mutually respectful relationship despite her young age, and Isabella went into mourning when Richard died three years later and refused to marry the son of his usurper (a brave move for a ten-year old alone in a foreign country). She ended up married for the second time at 16 and this time died at 19 - you guessed it, in childbirth. Nineteen is a much more reasonable age for childbirth, though, so really Isabella was just incredibly unfortunate.
The counter to this is a famous example - Margaret Beaufort, mother of Henry VII. She was married for the first time somewhere between 1-3 years old, although she never formally recognised the marriage and technically it wasn't binding in canon law since she was under 12. She married 24-year old Edmund Tudor when she was 12, and Edmund did consummate the marriage. Yeah, feel free to be grossed out. If it helps, he later died of bubonic plague, a particularly nasty way to go - leaving behind a 13-year old widow who was seven months pregnant. Margaret is the perfect case for demonstrating why people generally didn't do this; she and her child both nearly died multiple times during labour, and the early pregnancy permanently damaged her reproductive organs. She never got pregnant again, despite two more marriages - one aged 15-28, and one aged 29 until her death aged 66. She's a particularly unfortunate case, and solid evidence for why this didn't happen very often.
The best way to see whether it was an unconsummated (at first) political marriage or not is probably to look at the dates of the births of their children. Teenagers, despite being utterly unsuited to carrying and birthing a child, tend to be fairly fertile, so if the marriage was consummated early then she'd tend to have her first child (or first miscarriage) fairly young.